Part 9

Professor Mosso, of Turin, has lately made some interesting experiments on persons who had lost portions of the cranial bones, using Marey's ingenious hydro-sphygmograph. Noting, like others before him, that during sleep the brain diminished in volume, with shrinkage of its blood-vessels, and that the lively blush characterizing its surface during the waking state disappeared, he observed also that any sudden impression, if sufficient to rouse the brain to partial activity, was sure to be attended with an increase of its vascularity and its volume. He has proved, too, that every effort of the intellect is normally accompanied by a diminution of volume in the peripheral parts, the arm, for example, and that, on the contrary, when the cerebral activity is lessened the distant members are augmented in volume. Sleep is always accompanied by a dilatation of the vessels of the extremities, and particularly of the forearm, where this dilatation has repeatedly been measured by Mosso with his registering apparatus. Every excitation from without causes a contraction of the vessels of the forearm of the sleeping subject, and the augmented blood pressure at once produces a renewed afflux of blood to the brain. In this manner the fluctuations of cerebral activity can be followed: a sound, a touch, a ray of light falling on the closed lid of the sleeper, all give rise to modifications of the cerebral circulation--unperceived, doubtless, but possibly the source of dreams.[11]

The immediate cause of sleep is not simply the shutting off of a portion of the blood current from the brain. There are more important factors. Here Vulpian[12] is right. The lessening of the blood supply to the encephalon is rather the accompaniment than the cause of sleep. We cannot produce normal sleep in a person simply by exsanguinating his brain, or else we should have in an ice-cap and a hot foot-bath the speediest and most effective of hypnotics. The brain must first be in a certain condition. There must be in the constitution of the supreme nerve centers something that forbids further activity, and with that cessation of activity there will be a lessening of the blood-flow to the brain, in accordance with the physiological law before stated. What is the particular modification of the cortical cells which renders them less fit for the liberation of their special forces, and finally compels a suspension of action, with a diminution of the blood supply? Herbert Spencer has given a very plausible explanation, in accordance with the theory of evolution:

The waste of the nerve-centers having become such that the stimuli received from the external world no longer suffice to call forth from them adequate discharges, there results a diminished impulse to those internal organs which subserve nervous activity, including more especially the heart. Consequently, the nerve-centers, already working feebly, are supplied with less blood and begin to work more feebly, responding still less to impressions, and discharge still less to the heart. And so the two act and react until there is reached a state of profound unimpressibility and inactivity. Between this state and the waking state the essential distinction is great reduction of waste, which falls so low that the rate of repair exceeds it.... During the day the loss is greater than the gain, whereas during the night the gain is diminished by scarcely any loss. Hence results accumulation; there is restoration of nerve-tissue to its state of integrity.

According to Mr. Spencer, that rhythmical variation in nervous activity which we see in sleep and waking is the result of adaptation, due to survival of the fittest. "An animal so constituted that waste and repair were balanced from moment to moment throughout the twenty-four hours would, other things equal, be overcome by an enemy or competitor that could evolve greater energy during the hours when light facilitates action, at the expense of being less energetic during the hours of darkness and concealment."[13]

With some qualification, the foregoing statement is about as satisfactory as any that has yet been offered as to the proximate cause of sleep. During the waking hours the vaso-motor center in the medulla is doubtless under inhibition by the superior centers, and there is relative relaxation of the cerebral arterioles, with dilatation of the capillaries; when the cells of the hemispheres are exhausted, they are no longer able to exercise this inhibition--in common parlance, they no longer powerfully extract the blood--and the vaso-motor center "puts on the brakes"; the blood supply is then no longer sufficient for function, though enough for nutrition.

An ingenious theory has lately been proposed by Preyer, of Jena,[14] according to which, to use a homely illustration, the fire ceases to burn because the flues are clogged with cinders.

As Preyer puts it, the activity of the cerebrum is a sort of respiration, while its repose is a sort of asphyxia of this organ. It is certain that every psychical act, every thought, involves a certain consumption of oxygen by the nervous substance. During waking, this gas is furnished to the brain in the blood. If the blood supply fails, those forms of activity which we denominate consciousness, attention, volition, and thought cease. This is easily proved by compression of the carotids. It is known that in the waking hours the muscles, as well as the nerves and the nerve-centers, as a consequence of that activity, produce substances easily oxidizable, among which is lactic acid. Some have even attributed the sense of fatigue which we experience after prolonged exertion to the presence of this acid in the blood.[15] According to Preyer, after the work of the day is done, and the quiet of sleep is sought, the waste materials of which we have spoken, and which he proposes to call _ponogènes_ (substances which cause fatigue), being accumulated in the tissues, little by little undergo decomposition, by taking oxygen from the blood. They thus divert a considerable quantity of this gas from the cerebrum, the cells of which, deprived of this element so indispensable to their activity, enter into a state of relative repose. These waste matters are, then, the physical cause of sleep, which will be the more profound and prolonged the more the blood is charged with the excrementitious products of function. Preyer has experimented on animals by injecting varying quantities of lactic acid into their blood, and has produced a deep somnolent condition which could not be distinguished from natural sleep. The use of lactate of sodium in the human subject has sometimes been attended with a like hypnotic effect. Further researches are needed before the question can be considered as settled.--_N. Y. Med. Jour._

* * * * *

PREPARATION OF CHLORHYDRINES.

The usual methods of preparing chlorhydrines are in part inconvenient, in part unsatisfactory in yield. A. Ladenburg therefore proposes the following process, using ethylen-chlorhydrine as an example:

Glycol is heated in a distillery apparatus to 148° C., and a _slow_ current of dry hydrochloric acid passed through it. The water formed and the glycol-chlorhydrine distill over and are collected in tubulated receivers. The temperature of the bath is gradually raised to 160° C., when all the glycol is completely decomposed, except a trifling residue. The distillate is mixed with two or three volumes of ether, and then freed from any hydrochloric acid present with potassium carbonate. The ethereal solution is drawn off, and completely dried over freshly fused potassium carbonate.--_Berl. Ber._

* * * * *

A NEW METHOD FOR THE DETECTION OF SUGAR IN THE URINE.

At a recent meeting of the Clinical Society of London, Dr. Oliver gave a demonstration of the method he employs for the detection of sugar in the urine by means of test-papers. The test-papers were charged with the carmine of indigo and carbonate of soda. When one was dropped into an ordinary half inch test tube, and as much water poured in as just covered the upper end, and heat applied, a transparent and true blue solution, resembling Fehling's in appearance, was obtained. (A transparent solution could not, at the meeting, be produced from the London water. The characteristic reaction with grape sugar was, however, unimpaired).

If with the paper one drop of diabetic urine had been added, shortly after the first simmer, a beautiful series of color changes appeared; first violet, then purple, then red, and finally straw color; while, on the other hand, one drop of non-diabetic urine induced no alteration of color. The colors returned in the inverse order on shaking the tube, which allowed the air to mingle with the liquid. Reheating restored the colors again.

Confirmation of the presence of glucose was obtained by dropping in a mercuric chloride paper, while the solution was still quite hot, after the complete development of the indigo reaction. Then there was produced immediately a blackish green precipitate. No such precipitation occurred when a drop of non-saccharine urine was under examination by the indigo test; then the blue solution was merely turned into a transparent green one.

This test, as Dr. Oliver pointed out, discovers (_a_) the normal sugar; (_b_) the varying proportions of sugar which fill in the gap between the normal amount and that which characterizes diabetes mellitus, as in liver derangements and vaso-motor disturbances; (_c_) diabetic proportions.

It possesses the following advantages over Fehling's test:

1. It will detect sugar in any proportion in the presence of albumen, peptone, blood, pus, or bile, and as readily as in ordinary diabetic urine.

2. It gives no play of colors with uric acid.

3. It possesses portability, cleanliness, and stability.

Moore's, Trommer's, and Boettger's bismuth tests are all inferior in delicacy.--_British Medical Journal._

* * * * *

CHEMICAL COMPOUNDS MADE BY COMPRESSION.

By M. W. SPRING.

The author has previously shown the possibility of uniting the fragments of solid bodies by the sole action of pressure. He also established at the same time the possibility of forming chemical compounds by means of pressure. Thus he obtained cuprous sulphide by compressing a mixture of sulphur dust and copper; mercuric iodide, by compressing mercuric chloride with potassium iodide, etc. Finally, by compressing in the same manner mixtures of the filings of different metals, he formed alloys having for equal compositions the same melting points as those obtained by fusion.

The last mentioned facts certainly establish the possibility of causing bodies to enter into chemical reaction by the mere agency of a mechanical energy. This result is closely linked with another obtained during the course of the same investigation: the polymerization of certain simple bodies, _e. g._, sulphur, by the action of pressure. The author had drawn a general conclusion from his experiments, and had announced that matter takes, below a given temperature, a state corresponding to the volume which it is compelled to occupy.

He has since undertaken a methodical study of the chemical reactions accomplished by the action of pressure. He had already shown the possibility of forming metallic arsenides by compressing mixtures of arsenic and of the filings of different metals (_Bulletin de l'Académie Royale de Belgique_, t. v., 1883), and he now communicates the results obtained by compressing mixtures of sulphur and of certain metals or non-metals. The results not merely confirm the author's former conclusions, but they throw a new light on the relations of organic and inorganic chemistry, and exhibit the so-called simple bodies as capable of assuming a peculiar constitution varying according to the conditions in which they are placed, and the actions to which they are submitted.

He used the metals in the state of fine filings immediately mixed with flowers of sulphur previously thoroughly washed. The mixtures were made in atomic proportions and were submitted to a preliminary pressure of 6,500 atmospheres. They then assumed the state of a hard compact mass, showing, on examination with the microscope, that the reaction of the sulphur and the metal had taken place wherever the elements were in contact. The mass obtained was then reduced into fine powder and compressed again from twice to eight times.

1. _Sulphur and Magnesium._--After six compressions there was obtained a gray mass with a feebly metallic surface luster. It dissolves in water at 50° to 60° with a slow escape of hydrogen sulphide, the liquid becoming of a golden yellow. A drop of hydrochloric acid occasions immediately a very strong escape of hydrogen sulphide, while free sulphur is deposited. Hence magnesium and sulphur combine under the action of pressure, forming magnesium sulphide and possibly a polysulphide.

2. _Sulphur and Zinc._--Three compressions yield a block deceptively similar to native blende with metallic luster. Dilute sulphuric acid dissolves the block slowly with an escape of hydrogen sulphide.

3. _Sulphur and Iron._--After four compressions a block is obtained which the file scarcely touches. Dilute sulphuric acid dissolves it easily with continuous escape of hydrogen sulphide. If the product of compression is heated in a closed tube no luminous phenomenon is observed, the body entering into tranquil fusion. Hence the potential heat of the free sulphur and iron has been realized during the compression.

4. _Sulphur and Cadmium._--Three compressions give a yellowish-gray homogeneous mass. The powder is yellow, but less pure than that of cadmium sulphide obtained by precipitation. Strong hydrochloric acid dissolves the mass with escape of hydrogen sulphide.

5. _Sulphur and Aluminum._--Result incomplete. After five compressions a mass is obtained which, in contact with moist air, gives off an odor of hydrogen polysulphide.

6. _Sulphur and Bismuth._--The combination takes place with great ease.

7. _Sulphur and Lead._--The combination is still more easy.

8. _Sulphur and Silver._--The action is slow; eight compressions are necessary.

9. _Sulphur and Copper._--Three compressions complete the combination. When the product of the compression is heated, there is no development of heat or light.

10. _Sulphur and Tin._--Three compressions give a block which yields a yellowish-gray powder, easily soluble in a hot solution of sodium sulphide. Stannic sulphide is therefore formed by the compression of sulphur and tin.

11. _Sulphur and Antimony._--After two compressions we obtain a gray-black mass having the color and luster of stibine. When powdered it dissolves with ease in hot hydrochloric acid, giving off hydrogen sulphide.

12. _Sulphur and Red Phosphorus; Sulphur and Carbon._--Result entirely _nil_; there is produced not the least trace of phosphorus sulphide nor of carbon sulphide.

CONCLUSIONS TO BE DRAWN FROM THESE FACTS.

The negative results just mentioned have an especial interest. It is established that red phosphorus has a higher specific gravity than white phosphorus, that of the former being 1.96, and that of the latter 1.82. The author's former researches (_Bulletins de l'Académie Royale de Belgique_, 49, p. 323, 1880) have shown that if sufficient pressure is applied to a body capable of assuming several allotropic states, it takes under pressure the state corresponding to its greatest density. It is consequently impossible to transform red phosphorus into white phosphorus by pressure. But we know, on the other hand, that red sulphur and red phosphorus may be mixed with impunity at common temperatures without combination ensuing; to produce combination the temperature must be raised to about 260°, the point of transformation of red phosphorus into white phosphorus.

It is thus established that red phosphorus must first be changed from its allotropic condition before entering into combination with sulphur. The pressure opposing this change renders also the act of combination impossible; red phosphorus appears to us like a body which has lost its chemical faculties.

Thus, the combination of an element with itself, _i. e._, its polymerization, has really the effect of extinguishing its energy, rendering it incapable of fulfilling certain functions. The chemistry of red phosphorus, more simple than that of white phosphorus, may be considered as the chemistry of a deadened body. The phosphorus which is found in combination with sulphur is phosphorus sulphides, and that which enters into combinations of other kinds, is certainly not phosphorus in the red state; it is even possible, if not probable, that it is not even white phosphorus, but a substance still unknown in the free state.

We arrive at a similar but more complete conclusion as to the nature of carbon. It is known that the affinity of carbon for sulphur and even for oxygen only becomes manifest at a temperature bordering upon redness. Is not this tantamount to saying that, in order to enter into combination with another body, carbon, like red phosphorus, must first change its allotropic condition? This view is supported by the following considerations: The specific heat of amorphous carbon, and, _a fortiori_, that of graphite and diamond, form exceptions to the law of Dulong and Petit; they are too small by more than one-half. They would be normal if the atomic weight of carbon were greater than it really is; in other words, free carbon were a polymer of combined carbon. Rose has found that at a temperature of about 500° the specific heat of carbon agrees with the law of Dulong and Petit. At this temperature carbon undergoes a beginning of depolymerization, _i. e._, its chemical affinities reappear, and it burns readily in oxygen. Do not these facts show a complete parallelism between the chemical history of phosphorus and that of carbon?

Crystalline carbon, and even free amorphous carbon, are without chemical activity at the ordinary temperature; but when, in consequence of a rise of temperature, they take another state, they are transformed into a new kind of carbon, constituting a fourth allotropic state, and endowed with a prodigious capacity of combination. If these conclusions are well founded, we may venture a step further and ask, if the carbon which enters into the composition, not of mere organic compounds, but of organized bodies, is not a carbon of still another allotropic state characterized by the appearance of new properties or forms of combination which find their expression in the vital phenomena.

In other words, a derivative of carbon, before forming part of a living body, must first undergo in its atoms a transformation similar to that which permits amorphous carbon to enter into the composition of organic compounds. In this order of ideas the carbon of organic chemistry would be merely a first deadened form of the carbon of biological chemistry, while free carbon is merely the defunct remains of the carbon of organic chemistry.--_Bulletin de la Société Chimique de Paris; Chem. News._

* * * * *

COPPER ALLOYS AMONG THE ANCIENTS.

By Prof. E. REYER, PH.D., of Vienna.

The earth's crust consists in part of eruptive rocks, in part of sedimentary rocks. Both of them have served from time immemorial for building purposes; but at a very early period they were the only source from which weapons and tools could be made. Subsequently metals became known, and were employed for this purpose.

Metals are rarely met with in a pure state, but generally in combination with oxygen or sulphur. If we examine the original material of which the earth was composed, and which is frequently injected through crevices in the earth's crust, and the superjacent sediment as eruptive rock, we find it to be a mixture of different substances of a complex nature. It contains silicon, aluminum, iron, calcium, magnesium, potassium, and sodium. None of these are in a free state, but are combined with oxygen. Silicon, the lighter metals, and heavy iron do not exhibit their true metallic character, having all been changed into stone-like compounds, "calcified by contact with vital air," as the old chemists expressed it.

Of the heavy metals that are of such importance to civilization I have only mentioned iron, for this alone, in its compounds, takes any considerable part in the rock formations. Other heavy metals are met with in smaller quantities in the rocks. They are scarcely taken into account by geologists who consider the earth as a whole, but it is these rare guests that are of the greatest importance to civilization.

The metals are met with as silicates in the eruptive masses; they are also found as oxides or sulphides, scattered through different eruptive rocks in small granules.[16] Besides these, the "ores," which are workable metallic compounds, are here and there concentrated in crevices or fissures, which exist in eruptive as well as in sedimentary rocks.

_Iron_ is met with as oxide in the eruptive rocks, in fissures, and finally in thick strata and deposits within the sediment; whole mountains consist of iron ore.

_Tin_ occurs as oxide (tin stone), scattered through eruptive masses rich in quartz, also in fissures.

_Copper_, combined with sulphur, is found distributed through dark eruptive rocks, poor in silica, and also in fissures in those regions.

_Gold_ and _silver_ are mixed in smaller quantities with ores of other metals.

All these are continually exposed to atmospheric agencies toward which they act very differently. The oxidized ores of iron and tin do not change their character. The sulphur compounds, at least when near the surface, are oxidized, and hand in hand with this process goes the partial reduction of certain metals to the metallic state. Gold and silver, and to a less extent copper, are subject to this change; they are unmasked and are exposed to day light, not as stones, but as brilliant, malleable metals. Finally, the heavy ores and metallic particles are loosened from the rocks by the destructive action of water, floated off, elutriated, and washed. In undisturbed mountain ranges the mineral treasures lie in masses before our eyes.

The native shining and malleable metals (gold, silver, and copper) naturally first attracted the attention of man. They may have used the separate nuggets for ornaments as they found them, or after hammering them together into plates. This was surely the first step in the use of metals. It can scarcely be supposed that this use of soft native metals contributed much to the progress of mankind, and it is highly probable that in those early times the noble metal had but little value. The shining particles, as long as the natural supply lasted, seemed like worthless tinsel. Copper, which can be made into tools and vessels, as well as soft, poor weapons, was more highly prized. Such materials were not, indeed, suitable and able to take the place of stone tools and weapons; nevertheless, this working of metals served as preparation for the more complicated work of later times. Man learned to hammer and shape metals, and he found out that the operation was much facilitated by heating the metal.

The discovery of iron meteorites may have had some value. In these the smith first became acquainted with the properties of a hard metal. But I would not attach too much importance to this. The art of working metals is not the possession of a people that have a few meteoric knives. In my opinion the metallurgical preparation of the hard metals from their ores is alone decisive on this point.

The volks' sagas frequently mention some god or hero, who discovered and taught metallurgy, yet there is scarcely any doubt that the "god," in most cases, was human ingenuity led by chance.