CHAPTER V.

OF VAN HELMONT AND THE IATRO-CHEMISTS.

Paracelsus first raised the dignity of chemistry, by pointing out the necessity of it for medical men, and by showing the superiority of chemical medicines over the disgusting decoctions of the Galenists. Libavius and Angelus Sala had carefully separated chemistry from the fanatical opinions of the followers of Paracelsus and the Rosecrucians. But matters were not doomed to remain in this state. Chemistry underwent a new revolution at this period, which shook the Spagirical system to its foundation; substituted other principles, and gave to medicine an aspect entirely new. This revolution was in a great measure due to the labours of Van Helmont.

John Baptist Van Helmont was a gentleman of Brabant, and Lord of Merode, of Royenboch, of Oorschot, and of Pellines. He was born in Brussels in 1577, and studied scholastic philosophy in Louvain till the age of seventeen. After having finished his _humanity_ (as it was termed), he ought, according to the usage of the place, to have taken his degree of master of arts; but, having reflected on the futility of these ceremonies, he resolved never to solicit any academical honour. He next associated himself to the Jesuits, who then delivered courses of philosophy at Louvain, to the great displeasure of the professors of that city. One of the most celebrated of the Jesuits, Martin del Rio, even taught him magic. But Van Helmont was disappointed in his expectations: instead of that true wisdom which he hoped to acquire, he met with nothing but scholastic dialectics, with all its usual subtilties. He was no better satisfied with the doctrines of the Stoics, who taught him his own weakness and misery.

At last the works of Thomas à Kempis, and John Taulerus fell into his hands. These sacred books of mysticism attracted his attention: he thought that he perceived that wisdom is the gift of the Supreme Being; that it must be obtained by prayer; and that we must renounce our own will, if we wish to participate in the influence of the divine grace. From this moment he imitated Jesus Christ, in his humility. He abandoned all his property to his sister, renouncing the privileges of his birth, and laying aside the rank which he had hitherto occupied in society. It was not long before he reaped the fruit of these abnegations. A genius appeared to him in all the important circumstances of his life. In the year 1633 his own soul appeared to him under the figure of a resplendent crystal.

The desire which he had of imitating in every respect the conduct of Christ, suggested to him the idea of practising medicine as a work of charity and benevolence. He began, as was then the custom of the time, by studying the art of healing in the writings of the ancients. He read the works of Hippocrates and Galen with avidity; and made himself so well acquainted with their opinions, that he astonished all the medical men by the profundity of his knowledge. But as his taste for mysticism was insatiable, he soon became disgusted with the writings of the Greeks; an accident led him to abandon them for ever. Happening to take up the glove of a young girl afflicted with the _itch_, he caught that disagreeable disease. The Galenists whom he consulted, attributed it to the combustion of the bile, and the saline state of the phlegm. They prescribed a course of purgatives which weakened him considerably, without effecting a cure. This circumstance disgusted him with the system of the humorists, and led him to form the resolution of reforming medicine, as Paracelsus had done. The works of this reformer, which he read with attention, awakened in him a spirit of reformation, but did not satisfy him; because his knowledge, being much greater than that of Paracelsus, he could not avoid despising the disgusting egotism, and the ridiculous ignorance of that fanatic. Though he had already refused a canonicate, he took the degree of doctor of medicine, in 1599, and afterwards travelled through the greatest part of France and Italy; and he assures us, that during his travels, he performed a great number of cures. On his return, he married a rich Brabantine lady, by whom he had several children; among others a son, afterwards celebrated under the name of Francis Mercurius, who edited his father’s works, and who went a good deal further than his father had done, in all the branches of theosophy. Van Helmont passed the rest of his life on his estate at Vilvorde, almost constantly occupied with the processes of his laboratory. He died in the year 1644, on the 13th of December, at six o’clock in the evening, after having nearly reached the age of sixty-seven years.

The system of Van Helmont has for its basis the opinions of the spiritualists. He arranged even the influence of evil genii, the efforts of sorcerers, and the power of magicians among the causes which produce diseases. The archeus of Paracelsus constituted one of the capital points of his theory; but he ascribed to it a more substantial nature than Paracelsus had done. This archeus is independent of the elements; it has no form; for form constitutes the object of generation, or of production. These ideas are obviously borrowed from the ancients. The _form_ of Aristotle is not the μορφη, but the ενεργεια (_the power of acting_) which matter does not possess.

The archeus draws all the corpuscles of matter to the aid of _fermentation_. There are, properly speaking, only two causes of things; the cause _ex qua_, and the cause _per quam_. The first of these causes is _water_. Van Helmont considered water as the true principle of every thing which exists; and he brought forward very specious arguments in favour of his opinion, drawn both from the animal and vegetable kingdom. The reader will find his arguments on the subject, in his treatise entitled “Complexionum atque Mistionum elementalium Figmentum.”[161] The only one of his experiments that, in the present state of our knowledge, possesses much plausibility, is the following: He took a large earthen vessel, and put into it 200 lbs. of earth, previously dried in an oven. This earth he moistened with rain-water, and planted in it a willow which weighed five pounds. After an interval of five years, he pulled up his willow and found that its weight amounted to 169 pounds, and about three ounces. During these five years, the earth in the pot was duly watered with rain or distilled water. To prevent the earth in which the willow grew from being mixed with new earth blown upon it by the winds, the pot was covered with tin plate, pierced with a great number of holes to admit the air freely. The leaves which fell every autumn during the vegetation of the willow in the pot, were not reckoned in the 169 lbs. 3 oz. The earth in the pot being again dried in the oven, was found to have lost about two ounces of its original weight. Thus 164 lbs. of wood, bark, roots, &c., were produced from water alone.[162] This, and several other experiments which it is needless to state, satisfied him that all vegetable substances are produced from water alone. He takes it for granted that fish live (ultimately at least) on water alone; but they contain almost all the peculiar animal substances that exist in the animal kingdom. Hence he concludes that animal substances are derived also from pure water.[163] His reasoning with respect to sulphur, glass, stone, metals, &c., all of which he thinks may ultimately be resolved into water, is not so satisfactory.

[161] J. B. Van Helmont, Opera Omnia, p. 100. The edition which I quote from was printed at Frankfort, in 1682, at the expense of John Justus Erythropilus, in a very thick quarto volume.

[162] Van Helmont, Opera Omnia, p. 104.

[163] Ibid., p. 105.

Water produces elementary earth, or pure quartz; but this elementary earth does not enter into the composition of organic bodies. Van Helmont excludes _fire_ from the number of elements, because it is not a substance, nor even the essential form of a substance. The matter of fire is compound, and differs entirely from the matter of light. Water gives origin also to the three chemical principles, salt, sulphur, and mercury, which cannot be considered as elements or active principles. I do not see clearly how he gets rid of _air_; for he says, that though water may be elevated in the form of vapour, yet that these vapours are no more air than the dust of marble is water.

According to Van Helmont, a particular disposition of matter, or a particular mixture of that matter is not necessary for the formation of a body. The archeus, by its sole power, draws all bodies from water, when the _ferment_ exists. This _ferment_, in its quality of a mean which determines the action of the archeus, is not a formal being; it can neither be called a _substance_, nor an _accident_. It pre-exists in the seed which is developed by it, and which contains in itself a second ferment of the seed, the product of the first. The ferment exhales an odour, which attracts the generating spirit of the archeus. This spirit consists in an _aura vitalis_, and it creates the bodies of nature in its own image, after its own _idea_. It is the true foundation of life, and of all the functions of organized bodies; it disappears only at the instant of death to produce a new creation of the body, which enters then, for the second time, into fermentation. The seed, then, is not indispensable to enable an animal to propagate its species; it is merely necessary that the archeus should act upon a suitable ferment. Animals produced in this manner are as perfect as those which spring from eggs.

When water, as an element, ferments, it develops a vapour, to which Van Helmont gave the name of _gas_, and which he endeavours to distinguish from _air_. This gas contains the chemical principles of the body from which it escapes in an aerial form by the impulse of the archeus. It is a substance intermediate between spirit and matter, the principle of action of life, and of generation of all bodies; for its production is the first result of the action of the vital spirit on the torpid ferment, and it may be compared to the _chaos_ of the ancients.

The term _gas_, now in common use among chemists, and applied by them to all elastic fluids which differ in their properties from common air, was first employed by Van Helmont: and it is evident, from different parts of his writings, that he was aware that different species of gas exist. His _gas sylvestre_ was evidently our _carbonic acid gas_, for he says, that it is evolved during the fermentation of wine and beer; that it is formed when charcoal is burnt in air; and that it exists in the Grotto del Cane. He was aware that this gas extinguishes a lighted candle. But he says that the gases from dung, and those formed in the large intestines, when passed through a candle, catch fire, and exhibit a variety of colours, like the rainbow.[164] To these combustible gases he gave the names of _gas pingue_, _gas siccum_, _gas fuliginosum_, or _endimicum_.

[164] De Flatibus, sect. 49. Opera Van Helmont, p. 405.

Sal ammoniac, he says, may be distilled alone, without danger, and so may aqua fortis (_aqua chrysulca_), but if they be mixed together so much gas sylvestre is produced, that the vessels employed, however strong, will burst asunder, unless an opening be left for the escape of this gas.[165] In the same way cream of tartar cannot be distilled in close vessels without breaking them in pieces, an opening must be left for the escape of the _gas sylvestre_, which is generated in such abundance.[166] He says, also, that when carbonate of lime is dissolved in distilled vinegar, or silver in nitric acid, abundance of gas sylvestre is extricated. From these, and many other passages which might be quoted, it is evident that Van Helmont was aware of the evolution of gas during the solution of carbonates and metals in acids, and during the distillation of various animal and vegetable substances, that he had anticipated the experiments made so many years after by Dr. Hales, and for which that philosopher got so much credit. But it would be going too far to say, as some have done, that Van Helmont knew accurately the differences which characterize the different gases which he produced, or indeed that he distinguished accurately between them. For it is evident, from the passages quoted and from many others which occur in his treatise, De Flatibus, that carbonic acid, protoxide of azote, and deutoxide of azote, and probably also muriatic acid gas were all considered by him as constituting one and the same gas. How, indeed, could he distinguish between different gases when he was not acquainted with the method of collecting them, or of determining their properties? These observations of Van Helmont, then, though they do him much credit, and show how far his chemical knowledge was superior to that of the age in which he lived, take nothing from the merit or the credit of those illustrious chemists who, in the latter half of the eighteenth century, devoted themselves to the investigation of this part of chemistry, at that time attended with much difficulty, but intimately connected with the subsequent progress which the science has made.

[165] Ibid., p. 408.

[166] Ibid., p. 409.

Van Helmont was aware, also, that the bulk of air is diminished when bodies are burnt in it. He considered respiration to be necessary in this way: the air was drawn into the blood by the pulmonary arteries and veins, and occasioned a fermentation in it requisite for the continuance of life.

Gas, according to Van Helmont, has an affinity with the principle of the movement of the stars, to which he gave the name of _blas_. It had, he supposed, much influence on all sublunary bodies. He admitted in the ferment which gives birth to plants, a substance which, after the example of Paracelsus, he called _pessas_, and to the metallic ferment he gave the name of _bur_.[167]

[167] In his Magnum Oportet, sect. 39, p. 151, he gives an account of the origin of metals in the earth, and in that section there is a description of _bur_, which those who are anxious to understand the ideas of the author on this subject may consult.

The archeus of Van Helmont, like that of Paracelsus, has its seat in the stomach. It is the same thing as the sentient soul. This notion of the nature and seat of the archeus was founded on the following experiment: He swallowed a quantity of _aconitum_ (_henbane_). In two hours he experienced the most disagreeable sensation in his stomach. His feeling and understanding seemed to be concentrated in that organ, for he had no longer the free use of his mental faculties. This feeling induced him to place the seat of understanding in the stomach, of volition in the heart, and of memory in the brain. The faculty of desire, to which the ancients had assigned the liver as its organ, he placed in the spleen. What confirmed him still more in the idea that the stomach is the seat of the soul, is the fact, that life sometimes continues after the destruction of the brain, but never, he alleges, after that of the stomach. The sentient soul acts constantly by means of the _vital spirits_, which are of a resplendent nature, and the nerves serve merely to moisten these spirits which constitute the mediums of sensation. By virtue of the archeus man is much nearer to the realm of spirits and the father of all the genii, than to the world. He thinks that Paracelsus’s constant comparison of the human body with the world is absurd. Yet Van Helmont, at least in his youth, was a believer in magnetism, which he employed as a method of explaining the effect of sympathy.

The archeus exercises the greatest influence on digestion, and he has chiefly the stomach and spleen under his superintendence. These two organs form a duumvirate in the body; for the stomach cannot act alone and without the concurrence of the spleen. Digestion is produced by means of an acid liquor, which dissolves the food, under the superintendence of the archeus. Van Helmont assures us that he had himself tasted this acid liquor in the stomach of birds. Heat, strictly speaking, does not favour digestion; for we see no increase of the digestive powers during the most ardent fever. Nor are the powers of digestion wanting in fishes, although they want the animal heat which is requisite for mammiferous animals. Certain birds even digest fragments of glass, which, certainly, simple heat would not enable them to do. The pylorus is, in some measure, the director of digestion. It acts by a peculiar and immaterial power, in virtue of a _blas_, and not as a muscle. It opens and shuts the stomach according to the orders of the archeus. It is in it, therefore, that the causes of derangement of digestion must be sought for.

The duumvirate just spoken of is the cause of natural sleep, which does not belong to the soul, as far as it resides in the stomach. Sleep is a natural action, and one of the first vital actions. Hence the reason why the embryo sleeps without ceasing. At any rate it is not true that sleep is owing to vapours which mount to the brain. During sleep the soul is naturally occupied, and it is then that the deity approaches most intimately to man. Accordingly, Van Helmont informs us, that he received in dreams the revelation of several secrets, which he could not have learnt otherwise.

The duumvirate operates the _first_ digestion, of which, Van Helmont enumerates six different species. When the acid, which is prepared for digestion, passes into the duodenum it is neutralized by the bile of the gall-bladder. This constitutes the second digestion. To the bile of the gall-bladder, Van Helmont gave the name of _fel_, and he carefully distinguished it from the biliary principle in the mass of the blood. This last he called _bile_. The _fel_ is not an excrementitious matter, but a humour necessary to life, a true vital balsam. Van Helmont endeavoured to show by various experiments that it is not _bitter_.

The _third_ digestion takes place in the vessels of the mesentery, into which the gall-bladder sends the prepared fluid. The _fourth_ digestion is operated in the heart, where the red blood becomes more yellow and more volatile by the addition of the vital spirits. This is owing to the passage of the vital spirit from the posterior to the anterior ventricle, through the pores of the septum. At the same time the pulse is produced, which of itself develops heat; but does not regulate it in any manner, as the ancients pretended that it did. The _fifth_ digestion consists in the conversion of the arterial blood into vital spirit. It takes place principally in the brain, but is produced also throughout all the body. The _sixth_ digestion consists in the elaboration of the nutritive principle in each member, where the archeus prepares its own nourishment by means of the vital spirits. Thus, there are six digestions: the number seven has been chosen by nature for a state of repose.

From the preceding sketch of the physiology of Van Helmont, it is evident that he paid little or no regard to the structure of the parts in explaining the functions. In his pathology we find the same passion for spiritualism. He admitted, indeed, the importance of anatomy, but he regretted that the pathological part of that science had been so little cultivated. As the archeus is the foundation of life and of all the functions, it is plain that the diseases can neither be derived from the four cardinal humours, nor from the disposition or the action of opposite things; the proximate cause of diseases must be sought for in the sufferings, the anger, the fear, and the other affections of the archeus, and their remote cause may be considered as the ideal seed of the archeus. Disease, in his opinion, is not a negative state or a mere absence of health, it is a substantial and active thing as well as a state of health. Most of the diseases which attack certain parts or members of the body result from an error in the archeus, who sends his ferment from the stomach in which he resides into the other parts of the body. Van Helmont explained in this way not only the epilepsy and madness, but likewise the _gout_, which does not proceed from a flux, and has not its seat in the limb in which the pain resides, but is always owing to an error in the vital spirit. It is true that the character of the gout acts upon the semen in which the vital spirit principally manifests its action, and that in this way diseases are propagated in the act of generation; but if, during life instead of altering the semen it is carried to the liquid of the articulations, this is a proof of the prudence of nature, which lavishes all her cares on the preservation of the species, and loves better to alter the humours of the articulations than the semen itself. The gout acidifies the liquors of the articulations, which is then coagulated by the acids. The duumvirate is the cause of apoplexy, vertigo, and particularly of a species of asthma, which Van Helmont calls _caducus pulmonalis_. Pleurisy is produced in a similar way. The archeus, in a movement of rage, sends acrid acids to the lungs, which occasion an inflammation. Dropsy is also owing to the anger of the archeus, who prevents the secretions of the kidneys from going on in the usual way.

Of all the diseases, fever appeared to him most conformable to his notions of the unlimited power of the archeus. The causes of fever are all much more proper to offend the archeus, than to alter the structure of parts and the mixture of humours. The cold fit is owing to a state of fear and consternation, into which the archeus is thrown, and the hot stage results from his disordered movements. All fevers have their peculiar seat in the duumvirate.

Van Helmont was in general much more successful in refuting the scholastic opinions by which the practice of medicine was regulated in his time, than in establishing his own. We are struck with the force of his arguments against the Galenical doctrine of fever, and against the influence of the cardinal humours on the different kinds of fever. He refuted no less vehemently the idea of the putridity of the blood, while that liquid circulates in the vessels. Perhaps he carried the opposite doctrine too far; but his opinions have had a good effect upon subsequent medical theory, and medical men learned from them to make less use of the term putridity. The phrase _mixture of humours_, not more intelligible, however, came to be substituted for it.

Van Helmont’s theory of urinary calculi deserves peculiar attention, because it exhibits the germ of a more rational explanation of these concretions than had been previously attempted by physiologists. Van Helmont was aware that Paracelsus, who ascribed these concretions to tartar, had formed an idea of their nature, which a careful chemical analysis would immediately refute. He satisfied himself that urinary calculi differ completely from common stones, and that they do not exist in the food or drink which the calculous person had taken. Tartar, he says, precipitates from wine, not as an earth, but as a crystallized salt. In like manner, the natural salt of urine precipitates from that liquid, and gives origin to calculi. We may imitate this natural process by mixing spirit of urine with rectified alcohol. Immediately an _offa alba_ is precipitated.

It is needless to observe that Van Helmont was mistaken, in supposing that this _offa_ was the matter of calculus. Spirit of urine was a strong solution of carbonate of ammonia. The alcohol precipitated this salt; so that his _offa_ was merely _carbonate of ammonia_. Nor is there the shadow of evidence that alcohol, as Van Helmont thought it did, ever makes its way into the mass of humours; yet his notion of the origin of calculi is not less accurate, though of course he was ignorant of the chemical nature of the various substances which constitute these calculi. From this reasoning Van Helmont was induced to reject the term _tartar_, employed by Paracelsus. To avoid all false interpretations he substitutes the word _duelech_, to denote the state in which the spirit of urine precipitates and gives origin to these calculous concretions.

As all diseases proceeded in his opinion from the archeus, the object of his treatment was to calm the archeus, to stimulate it, and to regulate its movements. To accomplish these objects he relied upon dietetics, and upon acting on the imaginations of his patients. He considered _certain words_ as very efficacious in curing the diseases of the archeus. He admitted the existence of the universal medicine, to which he gave the names of _liquor alkahest_, _ens primum salium_, _primus metallus_. Mercurials, antimonials, opium, and wine, are particularly agreeable to the archeus, when in a state of delirium from fever.

Among the mercurial preparations, he praises what he calls _mercurius diaphoreticus_ as the best. He gives no account of the mode of preparing it; but from some circumstances I think it must have been _calomel_. He considers it as a sovereign remedy in fevers, dropsies, diseases of the liver, and ulcers of the lungs. He employed the red oxide of mercury as an external application to ulcers. The principal antimonial preparations which he employed were the hydrosulphuret, or _golden sulphur_, and the deutoxide, or _antimonium diaphoreticum_. This last medicine was used in scruple doses--a proof of its great inertness compared with the protoxide of antimony.

Opium he considered as a fortifying and calming medicine. It contains an acrid salt and a bitter oil, which give it the virtue of putting a stop to the errors of the archeus, when it was sending its acid ferment into other acid parts of the body. Van Helmont assures us that he wrought many important cures by the employment of wine.

Such is a very short statement of the opinions of a man, who, notwithstanding his attachment to the fanatical opinions which distinguished the time in which he lived, had the merit of overturning a vast number of errors, both theoretical and practical; and of laying down many principles, which, for want of erudition, have been frequently assigned to modern writers. Van Helmont has been frequently placed on the same level with Paracelsus, and treated like him with contempt. But his claims upon the medical world are much higher, and his merits infinitely greater. His notions, it is true, were fanatical; but his erudition was great, his understanding excellent, and his industry indefatigable. His writings did not become known till rather a late period; for, with the exception of a single tract, they were not published till 1648, by his son, after his death.

The decided preference given to chemical medicines by Van Helmont, and the uses to which he applies chemical theory, had a natural tendency to raise chemistry to a higher rank in the eyes of medical men than it had yet reached. But the man to whom the credit of founding the iatro-chemical sect is due, is Francis de le Boé Sylvius, who was born in the year 1614. While a practitioner of medicine at Amsterdam, he studied with profound attention the system of Van Helmont, and the rival and much more popular theory of Descartes: upon these he founded his own theory, which, in reality, contains little entitled to the name of original, notwithstanding the tone in which he speaks of it, and his repeated declarations that he had borrowed from no one. He was appointed professor of the theory and practice of medicine in the University of Leyden, where he taught with such eclat, and drew after him so great a number of pupils, that Boerhaave alone surpassed him in this respect. It was he that first introduced the practice of giving clinical lectures in the hospitals, on the cases treated in the presence of the pupils. This admirable innovation has been productive of much benefit to medicine. He greatly promoted anatomical studies, and inspected, himself, a vast number of dead bodies. This is the more remarkable, because his own system, like that of Van Helmont, from whom it was borrowed, was quite independent of the structure of the parts.

Every thing was explained by him according to the principles of chemistry, as they were then understood. The celebrity of the university in which he taught, and the vast number of his pupils, contributed to spread this theory into every part of the world, and to give it an eclat which is really surprising, when we consider it with attention. But he possessed the talents just suited for securing the reception of his opinions by his pupils as infallible oracles, and of being the idol of the university. Yet it is melancholy to be obliged to add, that few persons ever more abused the favours of nature, or the advantages of situation and elocution.

To form a clear idea of the principles of this founder of iatro-chemistry, we have only to call to mind the ferments of Van Helmont, which constitute the foundation-stone of the whole system. We cannot, says he, conceive a single change in the mixture of the humours, which is not the consequence of fermentation; and yet he assigns to this fermentation conditions which are scarcely to be found united in the living body. Digestion, in his opinion, is a true fermentation produced by the application of a ferment. Like Van Helmont, he admits a _triumvirate_; but places it in the humours; the effervescence or fermentation of which enabled him to explain most of the functions of the body. Digestion is the result of the mixture of the saliva with the pancreatic juice and the bile, and the fermentation of these humours. The saliva, as well as the pancreatic juice, contains an acidulous salt easily recognised by the taste. Here Sylvius derives advantage from the experiments of Regnier de Graaf on the pancreatic juice, which he had constantly found acid.

Sylvius, who affirmed that the bile contained an alkali, united with an oil and a volatile spirit, supposes an effervescence from the union of the alkali of the bile with the acid of the pancreatic juice, and this _fermentation_ he considered as the cause of digestion. By this fermentation the _chyle_ is produced, which is nothing else than the _volatile spirit_ of the food accompanied by an _oil_ and an alkali, neutralized by a weak acid. The blood is more than completed (_plus quam perficitur_) in the spleen. It acquires its highest perfection by the addition of a certain quantity of vital spirits. The _bile_ is not drawn from the blood in the liver, but pre-exists in the circulating fluid. It mixes with that fluid anew to be carried to the heart together with the _lymph_, equally mixed with the blood, and there it gives origin to a vital fermentation. In this way the blood becomes the centre of reunion of all the humours of the secretions, which mix together or separate, without the solids taking the smallest share in the operations. Indeed, so completely are the solids banished from the system of Sylvius that he attends to nothing whatever except the humours.

The formation and motion of the blood is explained by the fermentation of the oily volatile salt of the bile, and the dulcified acid of the lymph, which develops the vital heat, by which the blood is attenuated and becomes capable of circulating. This vital fire, quite different from ordinary fire is kept up in its turn by the uniform mixture of the blood. It attenuates the humours, not because it is _heat_ but because it is composed of _pyramids_. This last notion is obviously borrowed from Descartes, just as the fermentation in the heart, as the cause of the motion of the blood, reminds us of the opinions of Van Helmont.

Sylvius explains the preparation of the vital spirits in the encephalos by distillation, and he finds a great resemblance between their properties and those of spirit of wine. The nerves conduct these spirits to the different parts, and they spread themselves in the substance of the organs to render them sensible. When they insinuate themselves into the glands the addition of the acid of the blood produces a liquid analogous to naphtha, which constitutes the _lymph_. Lymph, then, is a compound of the vital spirit and the acid of the blood. _Milk_ is formed in the mammæ by the afflux of a very mild acid, which gives a white colour to the red humour of the blood.

The theory of the natural functions was no less chemical. Even the diseases themselves were explained upon chemical principles. Sylvius first introduced the word _acridity_ to denote a predominance of the chemical elements of the humours, and he looked upon these _acridities_ as the proximate cause of all diseases. But as every thing acrid may be referred to one or other of two classes, acids and alkalies, there are only two great classes of diseases; namely, those proceeding from an _acid acridity_, and those proceeding from an _alkaline_.

Sylvius was not altogether ignorant of the constituent parts of the animal humours; but it is obvious, from the account of his opinions just given, that this knowledge was very incomplete; indeed the whole of his chemical science resolves itself into a comparison of the humours of the living body with chemical liquids. Perhaps his notions respecting such of the _gases_, as he had occasion to observe, were somewhat clearer than those of Van Helmont. He called them _halitus_, and takes some notice of their different chemical properties, and states the influence which he supposes them to exert in certain diseases.

In the human body he saw nothing but a magna of humours continually in fermentation, distillation, effervescence, or precipitation; and the physician was degraded by him to the rank of a distiller or a brewer.

Bile acquires different acridities, when bad food, altered air, or other similar causes act apon the body. It becomes _acid_ or _alkaline_. In the former case it thickens and occasions obstructions; in the latter it excites febrile heat; and the viscid vapours elevated from it are the cause of the cold fit with which fever commences. All acute and continued fevers have their origin in this acridity of the bile. The vicious mixture of the bile with the blood, or its specific acridity, produces _jaundice_, which is far from being always owing to obstructions in the liver. The vicious effervescence of the bile with the pancreatic juice produces almost all other diseases. But all these assertions of Sylvius are unsupported by evidence.

The acid acridity of the pancreatic juice, and the obstruction of the pancreatic ducts, which are produced by it, are considered by him as the cause of intermittent fevers. When the acid of the pancreatic juice acquires still more acridity, hypochondriasis and hysteria are the consequences of it. If, during the morbid effervescence of the pancreatic juice with the bile an acid and viscid humour arise, the vital spirits of the heart are overwhelmed during a certain time. This occasions syncope, palpitation of the heart, and other nervous affections.

When the acid acridity of the pancreatic juice or of the lymph (for both are similar) is deposited on the nerves, the consequence is spasms or convulsions; epilepsy in particular depends upon the acrid vapours produced by the morbid effervescence of the pancreatic juice with acrid bile. Gout has the same origin as intermittent fevers, for we must look for it in the obstruction of the pancreas and the lymphatic glands, accompanied with an acid acridity of the lymph. Rheumatism is owing to the acrid acid, deprived of the oil which dulcifies it. The smallpox is occasioned by an acid acridity in the lymph, which gives origin to the pustules. Indeed all suppuration in general is owing to a coagulating acid in the lymph. Syphilis results from a caustic acid in the lymph. The itch is produced by an acid acridity of the lymph. Dropsies are produced by the same acid acridity of the lymph. Urinary calculi are the consequences of a coagulating acid existing in the lymph and the pancreatic juice. Corrosive acids, and the loss of volatile spirits, occasion leucorrhœa.

From the preceding statement it would appear that almost all diseases proceed from acids. However, Sylvius informs us that malignant fevers are owing to a superabundance of volatile salts and to a too great tenuity of the blood. The vital spirits themselves give occasion to diseases. They are sometimes too aqueous, sometimes they effervesce too violently, and sometimes not at all. Hence all the nervous diseases, which Sylvius never considers as existing by themselves; but as always derived from the acid, acrid, or alkaline vapours which trouble the vital spirits.

The method of cure which Sylvius deduced from these absurd and contemptible hypotheses, was worthy of the hypotheses themselves; and certainly constitute the most detestable mode of treatment that ever has disgraced medical science. To diseases produced by the effervescence of the bile he opposed purgatives; because in his opinion emetics produced injurious effects. The reason was, that the emetics which he employed were too violent, consisting of antimonial preparations, particularly _powder of Algerotti_, or an impure protoxide of antimony. For though _emetic tartar_ had been discovered in 1630, it does not seem to have come into use till a much later period. We do not find any notice of it in the _praxis chymiatrica_ of Hartmann published in 1647, at Geneva.

He endeavoured to moderate the acridity of the bile by opiates and other narcotics. It will scarcely be believed, though it was a natural consequence of his opinions, when we state that he recommended ammoniacal preparations, particularly his oleaginous volatile salt, and spirit of hartshorn, &c., as cures for almost all diseases. Sometimes they were employed to correct the acidity of the lymph, sometimes to destroy the acid acridity of the pancreatic juice, sometimes to correct the inertness of the vital spirits, sometimes to promote the secretions, and to induce a flow of the menses. Volatile spirit of amber and opium were prescribed by him in intermittent fevers; and volatile salts in almost all acute diseases. He united them with antivenomous potions, angelica, contrayerva, bezoard, crabs’ eyes, and other similar substances. These absorbents seemed to him very necessary to correct the acidity of the pancreatic juice, and the acridity of the bile. In administering them he paid no attention to the regular course which acute diseases usually run; he neither inquired into the remote nor proximate causes of disease, nor to the symptoms: every thing was neglected connected with induction, and his whole proceedings regulated by wild speculations and absurd theories, quite inconsistent with the phenomena of nature.

To attempt to refute these wild notions of Sylvius would be loss of time. It is extraordinary, and almost incredible, that he could have regulated his practice by them: and it is a still more incredible thing, and exhibits a very humiliating view of human nature, that these crudities and absurdities were swallowed with avidity by crowds of students, who placed a blind reliance on the dogmas of their master, and were initiated by him into a method of treating their patients, better calculated than any other that could easily have been devised, to aggravate all their diseases, and put an end to their lives. If any of the patients of the iatro-chemists ever recovered their health, well might it be said that their recovery was not the consequence of the prescriptions of their physicians, but that it took place in spite of them.[168]

[168] As an example of the prescriptions of Sylvius, we give the following for malignant fever:

_R._ Theriac. veter. ᴣij Antim. diaphor. ᴣj Syrup. Card. Benedic. ℥ij Aq. prophylact. ℥j -- Cinnam. ℥ss -- Scabios. ℥ij M. D.

It is a very remarkable circumstance, and shows clearly that mankind in general had become disgusted with the dogmas of the Galenists, that iatro-chemistry was adopted more or less completely by almost all physicians. There were, indeed, a few individuals who raised their voices against it; but, what is curious and inexplicable, they never attempted to start objections against the principles of the iatro-chemists, or to point out the futility of their hypothesis, and their inconsistency with fact. They combated them by arguments not more solid than those of their antagonists.

During the presidency of Riolan over the Medical College of Paris, that learned body set itself against all innovations. Guy Patin, who was a medical professor in the University of Paris, and a man of great celebrity, opposed the chemical system of medicine with much zeal. In his Martyrologium Antimonii he collects all the cases in which the use of antimony, as a medicine, had proved injurious to the patient. But in the year 1666, the dispute relative to antimony, and particularly relative to tartar emetic, became so violent, that all the doctors of the faculty of Paris were assembled by an order of the parliament, under the presidency of Dean Vignon, and after a long deliberation, it was concluded by a majority of ninety-two votes, that tartar emetic, and other antimonials, should not only be permitted, but even recommended. Patin after this decision pretended no longer to combat chemical medicine; but he did not remain inactive. One of his friends, Francis Blondel, demanded the resolution to be cancelled; but his exertions were unsuccessful; nor were the writings of Guillemeau and Menjot, who were also keen partisans of the views of Patin, attended with better success.

In England iatro-chemistry assumed a direction quite peculiar. It was embraced by a set of men who had cultivated anatomy with the most marked success, and who were quite familiar with the experimental method of investigating nature. The most eminent of all the English supporters of iatro-chemistry was Thomas Willis, who was a contemporary of Sylvius.

Dr. Willis was born at Great Bodmin, in Wiltshire, in 1621. He was a student at Christchurch College, in Oxford, when that city was garrisoned for King Charles I. Like the other students, he bore arms for his Majesty, and devoted his leisure hours to the study of physic. After the surrender of Oxford to the parliament, he devoted himself to the practice of medicine, and soon acquired reputation. He appropriated a room as an oratory for divine service, according to the forms of the church of England, to which most of the loyalists of Oxford daily resorted. In 1660, he became Sedleian professor of natural philosophy, and the same year he took the degree of doctor of physic. He settled ultimately in London, and soon acquired a higher reputation, and a more extensive practice, than any of his contemporaries. He died in 1675, and was buried in Westminster Abbey. He was a first-rate anatomist. To him we are indebted for the first accurate description of the brain and nerves.

But it is as an iatro-chemist that he claims a place in this work. His notions approach nearer to those of Paracelsus than to the hypotheses of Van Helmont and Sylvius. He admits the three chemical elements of Paracelsus, salt, sulphur, and mercury, in all the bodies in nature, and employs them to explain their properties and changes; but he gives the name of _spirit_ to the _mercury_ of Paracelsus. He ascribes to it the virtue of volatilizing all the constituent parts of bodies: salt, on the other hand, is the cause of fixity in bodies; _sulphur_ produces colour and heat, and unites the _spirit_ to the _salt_. In the stomach there occurs an acid ferment, which forms the chyle with the sulphur of the aliments: this chyle enters into effervescence in the heart, because the salt and sulphur take fire together. From this results the vital flame, which penetrates every thing. The vital spirits are secreted in the brain by a real distillation. The vessels of the testes draw an elixir from the constituent parts of the blood; but the spleen retains the earthy part, and communicates a new igneous ferment to the circulating fluid. On this account the blood must be considered as a humour, constantly disposed to fermentation, and in this respect it may be compared to wine. Every humour in which salt, sulphur, and spirit predominates in a certain manner, may be converted into a _ferment_. All diseases proceed from a morbid state or action of this ferment; and a physician may be compared to a wine-merchant; for, like him, he has nothing to do but to watch that the necessary fermentations take place with regularity, and that no foreign substance come to derange the operation.

At this period the mania of explaining every thing had proceeded to such a length, that no distinction was made between dead and living bodies. The chemical facts which were at that time known, were applied without hesitation to explain all the functions and all the diseases of the living body. According to Willis, fever is the simple result of a violent and preternatural effervescence of the blood and the other humours of the body, either produced by external causes, or by internal ferments, into which the chyle is converted when it mixes with the blood. The effervescence of the vital spirits is the source of quotidians; that of salt and sulphur produces continued fever; and external ferments of a malignant nature produce malignant fevers. Thus the smallpox is owing to the seeds of fermentation set in activity by an external principle of contagion. Spasms and convulsions are produced by an explosion of the salt and sulphur with the animal spirits. Hypochondriacal affections and hysteria depend originally on the morbid putrifaction of the blood in the spleen, or on a bad fermentescible principle, loaded with salt and sulphur, which unites with the vital spirits and deranges them. Scurvy is owing to an alteration of the blood, which may then be compared to vapid or stale wine. The gout is merely the coagulation of the nutritive juices altered by the acidified animal spirits; just as sulphuric acid forms a coagulum with carbonate of potash.

The action of medicines is easily explained by the effects which they produce on the nourishing principles. Sudorifics are considered as cordials, because they augment the sulphur of the blood, which is the true food of the vital flame. Cordials purify the animal spirits, and fix the too volatile blood. Willis disagrees with the other iatro-chemists of his time in one thing: he recommends bleeding in the greater number of diseases, as an excellent method of diminishing unnatural fermentation.

Dr. Croone, a celebrated Fellow of the Royal Society, was another English iatro-chemist, who attempted to explain muscular motion by the effervescence of the nervous fluid, or animal spirits.

It is not worth while to notice the host of writers--English, French, Italian, Dutch, and German, who exerted themselves to maintain, improve, and defend, the chemical doctrines of medicine. The first person who attempted to overturn these absurd doctrines, and to introduce something more satisfactory in their place, was Mr. Boyle, at that time in the height of his celebrity.

Robert Boyle was born at Youghall, in the province of Munster, on the 25th of January, 1627. He was the seventh son, and the fourteenth child of Richard, Earl of Cork. He was partly educated at home, and partly at Eton, where he was under the tuition of Sir Henry Wotton. At the age of eleven, he travelled with his brother and a French tutor through France to Geneva, where he pursued his studies for twenty-one months, and then went to Italy. During this period, he acquired the French and Italian languages; and, indeed, talked in the former with so much fluency and correctness, that he passed, when he thought proper, for a Frenchman. In 1642, his father’s finances were deranged, by the breaking out of the great Irish rebellion. His tutor, who was a Genevese, was obliged to borrow, on his own credit, a sum of money sufficient to carry him home. On his arrival, he found his father dead; and, though two estates had been left to him, such was the state of the times, that several years elapsed before he could command the requisite sum of money to supply his exigencies. He retired to an estate at Stalbridge, in Dorsetshire.

In 1654 he went to Oxford, where he associated himself with a number of eminent men (Dr. Willis among others), who had constituted themselves into a combination for experimental investigations, distinguished by the name of the _Philosophical College_. This society was transferred to London; and, in 1663, was incorporated by Charles II. under the name of the _Royal Society_. In 1668 Mr. Boyle took up his residence in London, where he continued till the last day of December, 1691, assiduously occupied in experimental investigations, on which day he died, in the sixty-fifth year of his age.

We are indebted to Mr. Boyle for the first introduction of the air-pump and the thermometer into Britain, and for contributing so much, by means of Dr. Hooke, to the improvement of both. His hydrostatical and pneumatical investigations and experiments constitute the foundation of these two sciences. The thermometer was first made an accurate instrument of investigation by Sir Isaac Newton, in 1701. This he did by selecting as two fixed points the temperatures at which water freezes and boils; marking these upon the stem of the thermometer, and dividing the interval between them into a certain number of degrees. All thermometers made in this way will stand at the same point when plunged into bodies of the same temperature. The number of divisions between the freezing and boiling points constitute the cause of the differences between different thermometers. In Fahrenheit’s thermometer, which is used in Great Britain, the number of degrees, between the freezing and boiling points of water, is 180; in Reaumur’s it is 80; in Celsius’s, or the centigrade, it is 100; and in De Lisle’s it is 150.

But my reason for mentioning Mr. Boyle here was, the attempt which he made in 1661, by the publication of his Sceptical Chemist, to overturn the absurd opinions of the iatro-chemists. He raises doubts, not only respecting the existence of the elements of the Peripatetics, but even of those of the chemists. The first elements of bodies, in his opinion, are _atoms_, of different shapes and sizes; the union of which gives origin to what we vulgarly call _elements_. We cannot restrain the number of these to four, as the Peripatetics do; nor to three, with the chemists: neither are they immutable, but convertible into each other. Fire is not the means that ought to be employed to obtain them; for the _salt_ and _sulphur_ are formed during its action by the union of different simple bodies.

Boyle shows, besides, that the chemical theory of qualities is exceedingly inaccurate and uncertain; because it takes for granted things which are very doubtful, and in many cases directly contrary to the phenomena of nature. He endeavours to prove the truth of these ideas, and particularly the production of the chemical principles, by a great number of convincing and conclusive experiments.

In another treatise, entitled “The Imperfections of the Chemical Doctrine of Qualities,”[169] he points out, in the second section, the insufficiency of the hypotheses of Sylvius relative to the generality of acids and alkalies. He shows that the offices ascribed to them are arbitrary, and the notions respecting them unsettled; that the hypotheses respecting them are needless, and insufficient, and afford but an unsatisfactory solution of the phenomena.

[169] Shaw’s Boyle, iii, 424.

These arguments of Boyle did not immediately shake the credit of the chemical system. In the year 1691, a chemical academy was founded at Paris by Nicolas de Blegny, the express object of which was to examine these objections of Boyle, which by this time had attracted great attention. Boyle’s experiments were repeated and confirmed; but the academicians, notwithstanding, came to the conclusion, that it is unnecessary to have recourse to the true elements of bodies; and that the phenomena which occur in the animal economy may be explained by the predominance of acids or alkalies. Various other publications appeared, all on the same side.

In Germany, Hermann Conringius, the most skilful physician of his time, opposed the chemical theory; and his opinions were impugned by Olaus Borrichius, who defended not only alchymy, but the chemical theory of medicine, with equal erudition and zeal.[170]

[170] De Ortu et Progressu Chemiæ. _Hafniæ_, 1674.

Towards the end of the sixteenth century, the chemists thought of examining the liquids of the living body, to ascertain whether they really contained the acids and alkalies which had been assigned them, and considered as the cause of all diseases. But at that time chemistry had made so little progress, and such was the want of skill of those who undertook these investigations, that they readily obtained every thing that was wanted to confirm their previous notions. John Viridet, a physician of Geneva, announced that he had found an acid in the saliva and the pancreatic juice, and an alkali in the gastric juice and the bile. But the most celebrated experiments of that period were those of Raimond Vieussens, undertaken in 1698, in order to discover the presence of an acid spirit in the blood. His method was, to mix blood with a species of clay, called _bole_, and to subject the mixture to distillation. He found that the liquid distilled over was acid. Charmed with this discovery, which he considered as of first-rate importance, he announced it by letter to the different academies and colleges in Europe. Some doubts being raised about the accuracy of his experiment, it having been alleged that the acid came from the clay which he had mixed with the blood, and not from the blood itself, Vieussens purified the _bole_ from all the acid which it could contain, and repeated his experiment again. The result was the same--the acrid salt of the fluid yielded an acid spirit.

It would be needless in the present state of our knowledge to point out the inaccuracy of such an experiment, or how little it contributed to prove that blood contains a free acid. It is now well known to chemists, that blood is remarkably free from acids; and, that if we except a little common salt, which exists in all the liquids of the human body, there is neither any acid nor salt whatever in that liquid.

Michael Ettmuller, at Leipsic, who was a chemist of some eminence in his day, and published a small treatise on the science, which was much sought after, was also a zealous iatro-chemist; but his opinions were obviously regulated by the researches of Boyle. He denies the existence of acids and alkalies in certain bodies, and distinguishes carefully between acid and putrid fermentation.

One of the most formidable antagonists to the iatro-chemical doctrines was Dr. Archibald Pitcairne, first a professor of medicine in the University of Leyden, and afterwards of Edinburgh, and one of the most eminent physicians of his time. He was born in Edinburgh, on the 25th of December, 1652. After finishing his school education in Dalkeith, he went to the University of Edinburgh, where he improved himself in classical learning, and completed a regular course of philosophy. He turned his attention to the law, and prosecuted his studies with so much ardour and intensity that his health began to suffer. He was advised to travel, and set out accordingly for the South of France: by the time he reached Paris he was so far recovered that he determined to renew his studies; but as there was no eminent professor of law in that city, and as several gentlemen of his acquaintance were engaged in the study of medicine, he went with them to the lectures and hospitals, and employed himself in this way for several months, till his affairs called him home.

On his return he applied himself chiefly to mathematics, in which, under the auspices of his friend, the celebrated Dr. David Gregory, he made uncommon progress. Struck with the charms of this science, and hoping by the application of it to medicine to reduce the healing art under the rigid rules of mathematical demonstration, he formed the resolution of devoting himself to the study of medicine. There was at that time no medical school in Edinburgh, and no hospital at which he could improve himself; he therefore repaired to Paris, and devoted himself to his studies with a degree of ardour that ensured an almost unparalleled success. In 1680 he received from the faculty of Rheims the degree of doctor of medicine, a degree also conferred on him in 1699 by the University of Aberdeen.

In the year 1691 his reputation was so high that the University of Leyden solicited him to fill the medical chair, at that time vacant; he accepted the invitation, and delivered a course of lectures at Leyden, which was greatly admired by all his auditors, among whom were Boerhaave and Mead. At the close of the session he set out for Scotland, to marry the daughter of Sir Archibald Stevenson: his friends in his own country would not consent to part with him, and thus he was reluctantly obliged to resign his chair in the University of Leyden.

He settled as a physician in Edinburgh, where he was appointed titular professor of medicine. His practice extended beyond example, and he was more consulted by foreigners than any Edinburgh physician either before or after his time. He died in October, 1713, admired and regretted by the whole country. He was a zealous supporter of iatro-mathematics, and as such a professed antagonist of the iatro-chemists. He refuted their opinions with much strength of reasoning, while his high reputation gave his opinions an uncommon effect; so that he contributed perhaps as much as any one, to put a period to the most disgraceful, as well as dangerous, set of opinions that ever overspread the medical horizon.

Into the merits of the iatro-mathematicians it is not the business of this work to enter; they at least display science, and labour, and erudition, and in all these respects are far before the iatro-chemists. Perhaps their own opinions were not more agreeable to the real structure of the human body, nor their practice more conformable to reason, or more successful than those of the chemists. Probably the most valuable of all Dr. Pitcairne’s writings, is his vindication of the claims of Hervey to the great discovery of the circulation.

Boerhaave, the pupil of Pitcairne, and afterwards a professor in Leyden, was a no less zealous or successful opponent of the iatro-chemists.

Herman Boerhaave, perhaps the most celebrated physician that ever existed, if we except Hippocrates, was born at Voorhout, a village near Leyden, in 1668, where his father was the parish clergyman. At the age of sixteen he was left without parents, protection, advice, or fortune. He had already studied theology, and the other branches of knowledge that are considered as requisite for a clergyman, to which situation he aspired; and while occupied with these studies he supported himself at Leyden by teaching mathematics to the students--a branch of knowledge to which he had devoted himself with considerable ardour while living in his father’s house. But, a report being raised that he was attached to the doctrines of Spinoza, the clamour against him was so loud that he thought it requisite to renounce his intention of going into _orders_.[171] He turned his studies to medicine, and the branches of science connected with that pursuit, and these delightful subjects soon engrossed the whole of his attention. In 1693 he was created doctor of medicine, and began to practise. He continued to teach mathematics for some time, till his practice increased sufficiently to enable him to live by his fees. His spare money was chiefly laid out upon books; he also erected a chemical laboratory, and though he had no garden he paid great attention to the study of plants. His reputation increased with considerable rapidity; but his fortune rather slowly. He was invited to the Hague by a nobleman, who stood high in the favour of William III., King of Great Britain; but he declined the invitation. His three great friends, to whom he was in some measure indebted for his success, were James Trigland, professor of theology, Daniel Alphen, and John Van den Berg, both of them successively chief magistrates of Leyden, and men of great influence.

[171] While travelling in a tract-boat, one of his fellow-travellers more orthodox than well informed, attacked the system of Spinoza with so little spirit, that Boerhaave was tempted to ask him if he had ever read Spinoza. The polemic was obliged to confess that he had not; but he was so much provoked at this public exposure of his ignorance, that he propagated the report of Boerhaave’s attachment to Spinozism, and thus blasted his intention of becoming a clergyman.

Van den Berg recommended him to the situation of professor of medicine in the University of Leyden, to which chair he was raised, fortunately for the reputation of the university, on the death of Drelincourt, in 1702. He not only gave public lectures on medicine, but was in the habit also of giving private instructions to his pupils. His success as a teacher was so great, that a report having been spread of his intention to quit Leyden, the curators of the university added considerably to his salary on condition that he would not leave them.

This first step towards fortune and eminence having been made, others followed with great rapidity. He was appointed successively professor of botany and of chemistry, while rectorships and deanships were showered upon him with an unsparing hand. And such was the activity, the zeal, and the ability with which he filled all these chairs, that he raised the University of Leyden to the very highest rank of all the universities of Europe. Students flocked to him from all quarters--every country of Europe furnished him with pupils; Leyden was filled and enriched by an unusual crowd of strangers. Though his class-rooms were large, yet so great was the number of students, that it was customary for them to keep places, just as is done in a theatre when a first-rate actor is expected to perform. He died in the year 1738, while still filling the three different chairs with undiminished reputation.

It is not our object here to speak of Boerhaave as a physician, or as a teacher of medicine, or of botany; though in all these capacities he is entitled to the very highest eulogium; his practice was as unexampled as his success as a teacher. It is solely as a chemist that he claims our attention here. His system of chemistry, published in two quarto volumes in 1732, and of which we have an excellent English translation by Dr. Shaw, printed in 1741, was undoubtedly the most learned and most luminous treatise on chemistry that the world had yet seen; it is nothing less than a complete collection of all the chemical facts and processes which were known in Boerhaave’s time, collected from a thousand different sources, and from writings equally disgusting from their obscurity and their mysticism. Every thing is stated in the plainest way, stripped of all mystery, and chemistry is shown as a science and an art of the first importance, not merely to medicine, but to mankind in general. The processes given by him are too numerous and too tedious to have been all repeated by one man, how laborious soever he may have been: many of them have been taken upon trust, and, as no distinction is made in the book, between those which are stated upon his own authority and those which are merely copied from others, this treatise has been accused, and with some justice, as not always to be depended on. But the real information which it communicates is prodigious, and when we compare it with any other system of chemistry that preceded it, the superiority of Boerhaave’s information will appear in a very conspicuous point of view.

After a short but valuable historical introduction he divides his work into two parts; the first treats of the _theory of chemistry_, the second of the _practical processes_.

He defines chemistry as follows: “Chemistry is an art which teaches the manner of performing certain physical operations, whereby bodies cognizable to the senses, or capable of being rendered cognizable, and of being contained in vessels, are so changed by means of proper instruments, as to produce certain determinate effects; and at the same time discover the causes thereof; for the service of various arts.”

This definition is not calculated to throw much light on chemistry to those who are unacquainted with its nature and object. Neither is it conformable to the modern notions entertained of chemistry; but it is requisite to keep in mind Boerhaave’s definition of chemistry, when we examine his system, that we may not accuse him of omissions and imperfections, which are owing merely to the state of the science when he gave his system to the world.

In his theory of chemistry he begins with the metals, which he treats of in the following order: Gold, mercury, lead, silver, copper, iron, tin. The account of them, though imperfect, is much fuller and more satisfactory than any that preceded it. He then treats of the salts, which are, common salt, saltpetre, borax, sal ammoniac and alum. This it will be admitted is but a meagre list. However other salts occur in different parts of the book which are not described here. He next gives an account of sulphur. Here he introduces _white arsenic_, obtained, he says, from cobalt, and not known for more than two hundred years. He considers it as a real sulphur, and takes no notice of metallic arsenic, though it had been already alluded to by Paracelsus. He then treats of bitumens, including under the name not merely bitumens liquid and solid, but likewise pit-coal, amber, and ambergris. An account of stones and earths comes next, and constitutes the most defective part of the book. It is very surprising that in this part of his work he takes no notice of _lime_. The semi-metals come next: they are, antimony, bismuth, zinc. Here he gives an account of the three vitriols or sulphates of iron, copper, and zinc. He knew the composition of sulphate of iron; but was ignorant of that of sulphate of copper and sulphate of zinc. He considers semi-metals as compounds of a true metal and sulphur, and therefore enumerates cinnabar among the semi-metals. Lastly he treats of vegetables and animals; and it is needless to say that his account is very imperfect.

He next treats of the utility of chemistry, and shows its importance in natural philosophy, medicine, and the arts. Afterwards he describes the instruments of chemistry. This constitutes the longest and the most important part of the whole work. He first treats of fire at great length. Here we have an account of the thermometer, of the expansion produced by heat, of steam, and in fact the germ of many of the most important parts of the science of heat, which have since been expanded and applied to the improvement, not merely of chemistry, but of the arts and resources of human industry. The experiments of Fahrenheit related by him, on the change of temperature induced by agitating water and mercury together at different degrees of heat, gave origin to the whole doctrine of specific heats. Though Boerhaave himself seemed not aware of the importance of these experiments, or indeed even to have considered them with any attention. But when afterwards analyzed by Dr. Black, these experiments gave origin to one of the most important parts of the whole science of heat.

He next treats at great length on _fuel_. Here his opinions are often very erroneous, from his ignorance of a vast number of facts which have since come to light. It is curious that during the whole of his very long account of combustion he makes no allusion to the peculiar opinions of Stahl on the subject; though they were known to the public, and had been admitted by chemists in general, before his work was published. To what are we to ascribe this omission? It could scarcely have been owing to ignorance, Stahl’s reputation being too high to allow his opinions to be treated with neglect. We must suppose, I think, that Boerhaave did not adopt Stahl’s doctrine of combustion; but at the same time did not think it proper to enter into any controversy on the subject.

He next treats of the heat produced when different liquids are mixed, as alcohol and water, &c. He gives many examples of such increase of temperature, and describes the phenomena very correctly. But he was unable to assign the cause of the evolution of this heat. The subject was elucidated many years after by Dr. Irvine, who showed that it was owing to a diminution of the specific heat which takes place when liquids combine chemically together. It is in this part of his work that he gives an account of phosphorus, of the action of nitric acid on volatile oils, and he concludes, from all the facts which he states, that elementary fire is a corporeal body. His explanation of the combustion of Homberg’s pyrophorus and of common phosphorus, shows clearly that he had no correct notion of the reason why air is necessary to maintain combustion, nor of the way in which that elastic fluid performs its part in the great phenomena of nature.

He next treats of the mode of regulating fire for chemical purposes: then he treats of _air_, his account being chiefly taken from Boyle. He ascribes the discovery of the law of the elasticity of air both to Boyle and Mariotte. Boyle, I believe, was the first discoverer of it. The French are in the habit of calling it the law of Mariotte. He then treats of _water_, and lastly of _earth_; but even here no mention whatever is made of lime. In the last part of the theory of chemistry he treats at great length of menstruums. These are water, oils, alcohol, alkalies, acids, and neutral salts. He mentions potash and ammonia, but takes no notice of soda; the difference between potash and soda not being accurately known. Nor can we expect any particular account of the difference between the properties of mild and caustic potash; as this subject was not understood till the time of Dr. Black. The only acids which he mentions are the _acetic_, _sulphuric_, _nitric_, _muriatic_, and _aqua regia_. He subjoins a disquisition on the alcahest or universal solvent, which it is obvious enough, however, from the way in which he speaks of it, that he was not a believer in. The object of his practical part is to teach the method of making all the different chemical substances known when he wrote. This he does in two hundred and twenty-seven processes, in which all the manipulations are described with considerable minuteness. This part of the work must have been long considered as of great utility, and must have been long resorted to by the student as a mine of practical information upon almost every subject that could arrest his attention. So immense is the progress that chemistry has made since the days of Boerhaave, and so different are the researches that at present occupy chemists, and so much greater the degree of precision requisite to be attained, that his processes and directions are now of little or no use to a practical student of chemistry, as they convey little or none of the knowledge which it is requisite for him to possess.

Boerhaave made a set of most elaborate experiments, to refute the ideas of the alchymists respecting the possibility of fixing mercury. He put a quantity of pure mercury into a glass vessel, and kept it for fifteen years at a temperature rather higher than 100°. It underwent no alteration whatever, excepting that a small portion of it was converted into a black powder. But this black powder was restored to the state of running mercury by trituration in a mortar. In this experiment the air had free access to the mercury. It was repeated in a close vessel with the same result, excepting that the mercury was kept hot for only six months instead of fifteen years.

To show that mercury cannot be obtained from metals by the processes recommended by the alchymists, he dissolved pure nitrate of lead in water, and, mixing the solution with sal ammoniac, chloride of lead precipitated. Of this chloride he put a quantity into a retort, and poured over it a strong lixivium of caustic potash, The whole was digested at the temperature of 96° for six months and six days. It was then distilled in a glass retort, by a temperature gradually raised to redness, but not a particle of mercury was evaporated, as it had been alleged by the alchymists would be the case.

Isaac Hollandus had stated that mercury could be easily obtained from the salt of lead made by means of distilled vinegar. To prove this he calcined a quantity of acetate of lead, ground the residue to powder, and triturated it with a very strong alkaline lixivium, and kept the lixivium over it covered with paper for months, taking care to add water in proportion as it evaporated. The calx was then distilled in a heat gradually raised to redness; but not a particle of mercury was obtained.[172]

[172] Mem. Paris, 1734, p. 539.

These were not the only laborious experiments which he made with this metal. He distilled it above five hundred times, and found that it underwent no alteration. When long agitated in a glass bottle it is convertible into a black acrid powder, obviously protoxide of mercury. This black powder, when distilled, is converted into running mercury. Exposure of mercury for some months in a heat of 180°, converts it also into protoxide; and if the heat be higher than this, the mercury is converted into a red acrid substance, obviously peroxide of mercury. But this peroxide, by simple distillation, is again reduced into the state of running mercury.[173]

[173] Phil. Trans. 1733. No. 430, p. 145.

Boerhaave combated the opinions of the iatro-chemists with great eloquence, and with a weight derived from his high reputation, and the extraordinary veneration in which his opinions were held by his disciples. His efforts were assisted by those of Bohn, who combated the medical opinions by arguments drawn both from experience and observation, and perfectly irresistible; and the ruin of the chemical sect was consummated by the exertions of the celebrated Frederick Hoffmann, the founder of the most perfect and satisfactory system of medicine that has ever appeared. His efforts were probably roused into action by a visit which he paid to England in 1683, during which he got acquainted with Boyle and with Sydenham; the former the greatest experimentalist, and the latter the greatest physician of the time; and both of whom were declared enemies to iatro-chemistry.