Part 4
73. I think, that from what occurs in the intestines we cannot infer what takes place in the pituitary and palatine membranes, &c.; because, although analogous, their organization may be different. In these parts we cannot examine the venous blood returning from them, as in the intestines: but, (1) If we consider, that in animals, which have for some time respired oxygen gas, the mucous membrane of the fauces does not exhibit any increase of redness; (2) If we bear in mind, that the lividity of different parts of this membrane, in those asphyxias which are produced by carbonic acid gas, is not occasioned by the immediate contact of this gas with the membranes, but by the reflux towards the surface, of the venous blood which cannot pass through the heart, as occurs in submersion, as demonstrated by Godwin, and as takes place in all those cases in which the blood, previous to death, has found difficulty in passing through the lungs; (3) If we remark lastly, that in these circumstances the contact of the air, after death, does not alter the lividity that the venous blood gives to the mucous membranes, although the skin is then more permeable to every kind of æriform fluid;--we shall see that we must at least suspend our judgment, respecting the colouring of the blood through mucous membranes, until farther observations shall have decided the question.
74. Observe another experiment, which may throw more light still upon the subject. I have distended the peritoneal cavity of different Guinea pigs with carbonic acid gas, with hydrogen gas, with oxygen gas, and with atmospheric air, to see if I could obtain, through a serous membrane, what I had not been able to effect through a mucous surface. In these experiments I have found no difference in the colour of the blood of the abdominal system: it was the same as in fresh animals of the same kind, that I always used to compare with those on which the experiments were made.
75. I believe, nevertheless, that I have observed many times, both in frogs and in animals with warm and red blood, such as cats and Guinea pigs, that the infiltration of oxygen gas into the cellular tissue gives, after a certain time, a brighter colour to the blood than this fluid presents in the artificial emphysemas which may be produced by carbonic acid gas, hydrogen gas, or by atmospheric air, in which circumstances the blood differs very little in colour from its natural shade. But in other cases oxygen gas has had no influence over the colour of the blood; so that, notwithstanding the many experiments that have been made on this point, I cannot state any general result. It appears, that the tonic powers of the cellular tissue, and of the coats of the vessels which ramify in it, receive a very varied influence from the contact of the gases, and that, according to the nature of that influence, the fibres contracting and becoming more or less firm render these parts more or less permeable, both to the æriform fluids, which have a tendency to escape from the blood to unite with that of the emphysema, and to this last fluid, if it tends to combine with the blood. This will doubtless explain the variations that I have observed.
76. Do the mucous surfaces exhale? The analogy of the skin would seem to lead to the belief of it; for it appears well proved, that the perspiration is not a transudation by the inorganic pores of the cutaneous surface, but a true transmission by vessels of a particular nature, and continuous with the arterial system.
77. It appears, at first, that the pulmonary perspiration which takes place on the surface of the bronchi, which has such connection with that of the skin, which increases or diminishes according to the decrease or augmentation of the other, and of which the composition is apparently of the same nature--it appears, I say, that the pulmonary perspiration is produced, at least in part, by the system of exhalent vessels; and that if the combination of the oxygen of the air concurs with the hydrogen of the blood to produce it, during the act of respiration, it is but in a very small quantity, and for that portion only which is purely aqueous. It is necessary to observe further on this subject, that the dissolution of the mucous fluid, which lubricates the bronchi, in the air that is constantly inspired and expired, furnishes a considerable portion of that vapour which rises from the lungs, and which is insensible in summer, but very apparent in winter.
78. The intestinal juice, that Haller has particularly considered, but which appears to be less in quantity than he had estimated, the gastric juice, and that of the œsophagus, are very probably disposed of by way of exhalation on their respective mucous surfaces; but in general it is very difficult to distinguish with precision, in these organs, what belongs to the exhalent system from what is furnished by the system of mucous glands, which, as we have said, are everywhere subjacent to them. Thus we constantly see the mucous fluids of the œsophagus, stomach, and intestines, mix themselves with the other fluids of these parts.
79. That mucous membranes absorb is evidently proved by the absorption of the chyle upon the intestinal surfaces, of venereal virus upon the glans and urethra, of variolous poison which is sometimes rubbed upon the gums, of the serous portions of the bile, of the urine, and of the semen, when they remain in their respective reservoirs. When, from paralysis of the fleshy fibres which terminate the rectum, the fæces accumulate at the extremity of that intestine (a very common case in aged persons, and of which Desault has cited many instances), these accumulations frequently become hard, probably from the absorption of their juices, which are obstructed there. We have many cases in which the urine has been almost entirely absorbed by the mucous surface of the bladder, when there has been absolute obstruction in the urethra. Whatever may be the mode of this absorption, it appears that it is not performed in a constant, uninterrupted manner, like that of the serous membranes, in which the exhalent and absorbent systems are in a continual alternate action; but that it occurs only under certain circumstances, of which perhaps the greatest part are not in the natural order of the functions. Finally, we have yet fewer data respecting the mode of mucous absorption than on that of cutaneous absorption: we confess it is very little understood, and many even question its existence.
SECTION X.
REMARKS ON THE AFFECTIONS OF MUCOUS MEMBRANES.
80. It is not my design to examine the affections of mucous membranes; I shall notice only some phenomena, which in these affections I believe deserve a particular attention, and the explanation of which I propose to physiological physicians.
81. Why do mucous membranes seldom contract adhesions from inflammation, since that occurs so frequently in serous surfaces under the same circumstances? Why does not the internal surface of the inflamed stomach, intestines, or bladder, adhere in its various portions like the pleura, tunica vaginalis, testis, &c.
82. Why, in inflammations of mucous membranes, is there an abundant flow of that fluid which habitually moistens them, and which constitutes the different kinds of catarrhs, whilst the source of the fluid that exhales from serous membranes is generally dried up in analogous cases?
83. Why do polypi, a kind of affection peculiar to mucous membranes, seldom arise but at the origins of these membranes in the vicinity of the skin, as in the nose, pharynx, vagina, &c., and not in their more internal portions, as in the stomach, intestines, &c.? Does this arise from the peculiarity of the texture that I have shown mucous membranes to have in the vicinity of those places where they arise from the skin, or must we attribute this fact to the more numerous causes of irritation which act upon the origins of these cavities?
84. Are not aphthæ an isolated inflammatory affection of the glands of the mucous membranes, whilst catarrhs are characterized by a general inflammation of all the parts of these membranes?
THE END.
CHARLES WOOD, Printer,
Poppin's Court, Fleet Street, London.
FOOTNOTES:
[A] The following questions have been much disputed: Is there a cystic and an hepatic bile? Is the one of a different nature from the other? Does their quantity increase or vary? &c. Contrary, and even opposite, opinions have been supported by numerous experiments made upon living animals, as Haller as well observed. These experiments, though at first sight contradictory, in reality are not so, as I have had the opportunity of convincing myself, by repeating them in the different stages of digestion, and during the abstinence of the animal, which previously had never been done with precision. The following are what I have observed in dogs that I have used in my experiments. (1) During abstinence, the stomach and the small intestines being empty, yellowish clear bile was found in the hepatic duct and ductus communis choledochus; the surface of the duodenum and jejunum were stained by a bile which had the same appearance; the gall bladder was very much distended by a greenish bitter bile, which was deeper in colour and more in quantity, according to the length of the abstinence. (2) During the gastric digestion, which may be prolonged for a sufficient length of time by giving the dog large pieces of meat, which he swallows without chewing, appearances were similar. (3) At the commencement of intestinal digestion, the bile in the hepatic duct was always found yellowish; that of the ductus communis choledochus deeper in colour; the gall bladder not so full, and its bile becoming already more clear. (4) Towards the end of digestion, and immediately after it, the bile of the hepatic duct, of the ductus communis choledochus, that contained in the gall bladder, and that which was spread over the duodenum, were exactly of the same colour as the common hepatic bile, a clear yellow, having but little bitterness. The gall bladder was but half full; it was not contracted, but flaccid.
These observations, repeated a great number of times, evidently prove, that such is the manner in which the bile flows during abstinence and during digestion. (1) It appears that the liver is continually separating from itself a sensible quantity of bile, which increases during digestion. (2) That which is secreted during abstinence is divided between the intestine, which is always found coloured with it, and the gall bladder, which retains it without transmitting any portion of it through the cystic duct, and where, thus retained, it acquires a deeper colour and a character of acrimony, necessary, without doubt, to the digestion which is soon to follow. (3) When the food, having been digested by the stomach, passes into the duodenum, then all the hepatic bile, which was before divided, flows into the intestine, and even in greater abundance; the gall bladder also pours that which it contains upon the alimentary pulp, and with which it is then found quite incorporated. (4) After the intestinal digestion the hepatic bile diminishes, and begins to flow, part into the duodenum and part into the gall bladder, where, being then examined, it is clear and in small quantity, because it has not yet had time either to become coloured, or to collect.
There is, therefore, this difference between the two kinds of bile, that the hepatic flows in a continual manner into the intestine, and the cystic, during the absence of digestion, flows back into the gall bladder; and whilst that function is going on it passes towards the duodenum; or rather it is always the same fluid, of which one part preserves the character it has when it leaves the liver, and the other part undergoes a change in the gall bladder. The difference of colour in the cystic bile, according to the time that it has remained in the gall bladder, is analogous to the colour of the urine, which becomes deeper as it is retained longer in its receptacle.
[B] The bile in the gall bladder, the urine in the bladder, and the semen in the vesicula seminales, are certainly absorbed; but it is not the fluid itself that re-enters the circulation, but only its finest parts, some of its principles that we are not well acquainted with, probably its aqueous or lymphatic portion. This does not resemble the absorption in the pleura and other analogous membranes, in which the fluid rejoins the blood in the same state as it left it.
[C] This is a necessary consequence of the disposition of the vascular system of the stomach. The arteria coronaria ventriculi superior being situated transversely between the stomach and the omentum, and furnishing branches to both, it is evident, that when the stomach, by separating the duplicatures of the omentum, lodges itself between them, and this in applying itself over the stomach becomes shortened, the branches that it receives from that artery cannot in the same manner apply themselves to it. To effect this it would be necessary, that they should proceed from the one to the other without the intermediate trunk that cuts them at right angles; then the stomach, by distending itself, would separate them in the same way that it does the omentum, and would lodge between them, instead of pushing them before it with their common trunk, and folding them upon themselves.
TRANSCRIBER'S NOTE
Italic text is denoted by _underscores_.
Obvious typographical errors and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources.
Except for those changes noted below, all misspellings in the text, and inconsistent or archaic usage, have been retained. For example, newly-born, newly born; circumvolutions; atmospherical.
Pg v (TOC), page '101' replaced by '98'. Pg 54, 'the mach, small' replaced by 'the stomach, small'. Pg 57, 'membranes is spread' replaced by 'membrane is spread'. Pg 81, 'OF THE SYMPATHY' replaced by 'OF THE SYMPATHIES'. Pg 86, 'fine pelicle' replaced by 'fine pellicle'. Pg 90, 'those asphyxies' replaced by 'those asphyxias'.