tion of the vessels of the skin is capable of being regulated independently of the cerebro-spinal vasomotor centers. It is not clear what is the nature of this mechanism, but it seems to be adequate to measure out the degree of dilatation according to the requirements of the tissues, and appears to be the same that is called into action under the application of irritants. The capillary vessels have been shown to be capable of varying their diameters independently of one another. The conclusion is logically derivable that each capillary is capable of varying its caliber in accordance with the requirements of the tissues which it supplies with blood. To this automatic regulation of the peripheral circulation Professor Ray is inclined to ascribe a function of great importance, both from a physiological and a pathological point of view; and it appears that it is principally, if not exclusively, in connection with it that the contractility of the capillaries comes into play.

Dr. J. N. Langley, of Trinity College, Cambridge, has brought the subject of the histology of the gastric or pepsin-making glands before the Royal Society, in a paper in which he has sought to collate the proofs, from his experiments, that the gastric glands in life contain no ferment, but much zymogen or substance capable of giving rise to ferment; that by far the greater part of the zymogen can be seen in the chief cells in the form of granules; and that during digestion the granules are usually used up in such a manner as to give rise to an outer non-granular and an inner granular zone in the chief cells. These points, if proved, would establish fundamental resemblances in life-habit between the chief cells of the gastric glands of mammals, the cells of the gastric glands of the lower vertebrates, and the cells of the pancreatic gland. It was found that the chief-cell granules of some mammals are preserved by osmic acid, while those of others are not. The examinations were made chiefly with preparations of the former class, and were checked by comparison with glands in the fresh state; they related to the border cells and the chief cells of different regions of the stomach. In both the mouse and the mole, in the hungry state, the chief cells are granular throughout; in the digestive state, the chief cells have an outer non-granular zone of from one third to one half of the cell. In the Gainea-pig and the rabbit the chief cells of the latter part of the greater curvature show few or no granules; in the median part of the greater curvature the glands have usually an outer clear zone, which diminishes in passing toward the fundus, while in the fundus and in the adjoining part of the greater curvature the chief cells are granular throughout. During digestion an outer clear zone is formed in the glands of the latter part of the fundus and the fore part of the greater curvature, while the cells of the rest of the greater curvature lose more or less completely their granules. Heidenhain first announced

the conclusion that the chief and not the border cells produce pepsin. This is confirmed by Dr. Langley's comparison of the pepsin contents of the different stomach regions in several animals. In each case the amount of pepsin found bore no relation to the number of border cells, but almost always varied directly with the number of chief cells. It was also shown that in the different regions of the stomach of the rabbit most pepsin is found where the granules are most numerous. It is now very generally accepted that pepsin exists in the gastric glands partly free and partly combined-i. e., partly as pepsin and partly as pepsinogen. A series of experiments made with especial reference to this point has convinced Dr. Langley that pepsin, as such, does not exist in the living glands, but that in the animals with which he worked, and probably in all vertebrates, the gastric glands store up pepsinogen and not pepsin. This is converted by hydrochloric acid into pepsin. As far as our knowledge goes, rennet - ferment is found in greatest quantity where there is most pepsin, and both vary pari passu. Perhaps, suggests Dr. Langley, the granules of the chief cells may contain zymogen both of pepsin and of rennet-ferment, and he offers this as a subject for further observation. In all the vertebrates in which the gastric glands have been carefully examined in the living state, it has been found that those gastric glands which produce most ferment store up their zymogen in the form of granules. The ferment-forming cells consist of a net-work of protoplasm, inclosing a mass of granules. It seems probable, on general grounds, that the cells should store up other antecedent substances besides zymogen, and we are not without facts which will tell in favor of this view. In the saliva of many animals ferment is almost or entirely absent, but mucin and proteids occur. We have some proof that mucin arises during secretion from the splitting up of an antecedent substance, mucigen, which is stored up in the cell; in the serous salivary glands, and in the lachrymal glands, the occurrence of granules which are used up during secretion, just as are the granules of the pancreas or of the gastric glands, makes it extremely probable that in those glands some antecedents of the proteids found in the secretion, not the actual proteids of the secretion, are stored up. Apparently, then, a large number of gland-cells have the feature in common that the cell protoplasm forms certain antecedent substances, which Dr. Langley proposes shall be called "mesostates," which it stores up, and that are converted, when secretion takes place, into secretory products. In the pancreas the chief mesostate is trypsinogen, in the gastric glands it is pepsinogen, in the mucous glands it is mucigen, etc.

Observations made by Uffelmann on a patient upon whom gastrotomy had been performed, have indicated that no hydrochloric acid is secreted during the earlier stages of

digestion, although that substance may sometimes be found in the course of three quarters of an hour or an hour after the ingestion of food. The acid present was always lactic, even when the conversion of albumen into peptone, and of starch into dextrine and sugar, was distinctly taking place. The observations of Cash, made in Ludwig's laboratory, have shown that, contrary to the statements usually given in text-books, fats may be split up in the stomach into the fatty acids and glycerine, while an acid, perhaps the lactic, is formed. It is a remarkable fact that although after the full digestion of every meal a considerable quantity of peptones must be introduced into the blood, none passes off by the kidneys; yet if solutions of the peptones be directly injected into the blood-vessels, from 60 to 70 per cent is rapidly eliminated by these organs. Hofmeister, finding peptone abundant in the wall of the intestine, has arrived at the conclusion, from his experiments on this point, that the numerous nuclei and cells which occupy the meshes of the adenoid tissue of the intestinal mucous membrane fix the peptones, and thus enable them to enter the bloodcurrent without the danger of being excreted by the kidneys. The white corpuscles, on this view, act as carriers of nutritive material to all parts of the body, just as the red corpuscles act as carriers of oxygen.

During digestion much saliva, gastric juice, and pancreatic juice flow into the alimentary canal, each secretion bearing with it a considerable quantity of ferment, chiefly either amylolytic or proteolytic. Very little, how ever, is known of the fate of these ferments; for the little of them that may be found in the fæces and urine makes but a small fraction of the whole amount which is received by the alimentary canal during digestion. Dr. J. M. Langley has made investigations on this subject, the results of which appear to him to show that the amylolytic ferment secreted by the salivary glands is destroyed by the hydrochloric acid of the gastric juice, that the proteolytic and rennet ferments secreted by the gastric glands are destroyed by the alkaline salts of the pancreatic and intestinal juices, and by trypsin, and that the proteolytic and amylolytic ferments secreted by the pancreas are not improbably destroyed in the large intestine by the acids formed there. In experiments with ptyalin, it was found that a ptyalin containing fluid capable of converting a considerable amount of starch into sugar in a few minutes is incapable, after treatment at 35° C. with hydrochloric acid of '04 per cent for seven hours, of converting any appreciable amount of starch into sugar in three hours. As in all the animals examined the fluid in the stomach reddened litmus-paper very much more deeply than does hydrochloric acid, the conclusion is drawn that the amylolytic ferment of the saliva is destroyed at any rate by the end of gastric digestion; and it was corroborated by

an experiment in which the diluted parotid extract retained but a trace of its amylolytic power when it was warmed for fifteen minutes with one tenth of its bulk of gastric fluid. The destructive action of even very dilute acids was found to be extraordinarily rapid. The secretions from the pancreas and intestinal glands are also capable of dissolving the gastric ferments, and owe their power chiefly to their alkaline salts. The action of these salts, as exemplified in sodium carbonate, is decided and rapid. It is augmented when trypsin is also present, but the effect of trypsin alone is less marked. The rennet ferment is, like pepsin, destroyed rapidly at the body temperature by sodium carbonate, and to some extent by trypsin; whence we may conclude that it also loses its ferment power irrecoverably in the small intestine. Since trypsin is destroyed both by hydrochloric acid and by pepsin, the adminis tration of pancreatic extract with food in medical practice to aid digestion is of more than doubtful benefit; for little, if any, trypsin can pass into the duodenum to exercise a digestive function there. An extract of the pancreas rapidly loses its amylolytic power when warmed with dilute hydrochloric acid, more rapidly than does trypsin under similar circumstances, but apparently less rapidly than does the amylolytic ferment of the parotid.

Recent researches reported by M. Dufresne throw new light on the relations of ptyalin, diastase, and the gastric juice. It has been a subject of debate whether the saliva is destroyed in the gastric juice, or continues in the stomach its action on starch. M. Dufresne's experiments prove that the saliva is paralyzed in pure gastric juice, but recovers its action in the mixed gastric juice and in the duodenum, and is capable of continuing the process of saccha rification; while diastase is irrecoverably destroyed in hydrochloric solutions or in pure gastric juice, and is profoundly altered after passing into the mixed gastric juice, so that if it still dissolves starch it no longer saccharifies it. Ptyalin is recommended as an excellent re-agent for demonstrating the difference between mixed gastric juice, which owes its acidity to organic acids, and pure gastric juice, the strength of which is derived from hydrochloric acid.

Seegen and Kratschner have brought a few new facts to light from their investigations of the relations of sugar to glycogen in the liver; and while they find, in accordance with most other observers, that the amount of sugar increases after death, they maintain that this increase does not take place, as is generally accepted, at the expense of the glycogen, but of some other substance; for not only does the quantity of sugar present augment, but a larger percentage of glycogen can actually in some instances be obtained some hours after the removal of the liver from the body than instantly after death. If this be true, and glycogen be the result of a process of disintegration, some

other compounds must also be present in larger quantities shortly after death. If these can be discovered, and their composition ascertained, it may hereafter be possible to trace the source of the glycogenous and saccharine bodies by a process of synthesis.

The lymphatics of the pancreas have been worked out and illustrated by Dr. and Mrs. Haggan. Sappey, of the Faculty of Medicine of Paris, has published a work on the morphological elements of the blood, in which he describes the red and white corpuscles of each division of the animal kingdom, and has illustrated them with many engravings. Crystallizable forms of albumen have been obtained from the seeds of the pumpkin and from hempseed, the latter presenting the octahedric and rhombic-dodecahedric forms that had been regarded as peculiar to hæmoglobin.

Professor Charles S. Ray, M. D., has applied to the investigation of the manner of action and the function of the spleen a method of indirect observation in which he studied the rapidity of the circulation through its blood-vessels. It is fully recognized by physiologists that, under normal conditions, a certain relation subsists between the degree of functional activity of an organ or tissue and the degree of expansion of its blood-vessels. Applying this rule to a series of observations on the kidney, he was surprised at the closeness of the correspondence that existed between the activity with which the renal circulation was carried on and the rapidity of the secretion of urine; which was so near that he found the rapidity of the flow of urine could be observed indirectly by watching the changes in the caliber of the blood-vessels of the kidney with much greater convenience than could be done directly by counting the number of drops of urine which escaped. It struck him that this method could be most usefully applied to the investigation of organs whose functions can not be studied by any direct method with which we are as yet acquainted, of which the spleen is a typical example; and it is conveniently situated for the purpose. His observations taught him that the circulation through the spleen differs from that of other organs in the important particular that the force which impels the blood through the organ is not that of the bloodpressure in the arteries, which has comparatively little influence on the volume of the spleen; but that the splenic circulation is car ried on chiefly, if not exclusively, by a rhtyhmic contraction of the muscles contained in the capsule and trabecula of the organ. The movement is exceedingly regular, in so far as rhythm is concerned, and varied but slightly during hours of experiment and under considerable changes of position. The process in the spleen is different in nature from the rhythmic contraction and expansion which may be observed in various organs on the "TraubeHering" blood-pressure curves showing themselves. The spleen also takes part in the pro

duction of these curves, but the contractions they indicate are readily distinguished from those which are proper to this organ and which are independent of changes in the blood-pressure. Stimulation either of the central end of a cut sensory nerve or of the medulla oblongata causes a rapid contraction of the spleen. Stimulation of the peripheral ends of both splanchnics and of both vagi causes a rapid contraction. After section of these four nerves, stimulation of a sensory nerve still causes a contraction, showing that vaso-constrictor influences may pass from the cerebro-spinal centers to the spleen by some other route or routes than the nerves named. The fact that the section of these principal nerves which convey vasomotor influences from the cerebro-spinal centers to the spleen has so little effect on the rhythmic contractions and expansions of the organ, seems to indicate that the latter are regulated and maintained by some mechanism contained in the spleen itself.

MM. H. Caillet de Poncy and C. Livron, or the Medical School at Marseilles, have found that, when poisoning by arsenic takes place, the phosphorus which exists as phosphoric acid in the brain is replaced by arsenic. The substitution takes place in the lecithine, a very complex nitrogenized compound, which thus becomes transformed into an insoluble albuminoid substance. Acute poisoning takes place too rapidly for the arseniated lecithine to be subjected to physiological reactions and be eliminated, and the animal dies under the local influence of the poison without sensible variation of the normal phosphorus of the nervous matter. In slow and chronic poisoning, the replacement is less rapid; arseniated lecithine is formed and acts as ordinary lecithine, passing gradually into the insoluble albuminoid state, while the phosphorus is steadily diminished, giving place to the arsenic.

Professor H. P. Bowditch and William F. Southard, M. D., of the Harvard Medical School, have performed a course of experiments to ascertain which of the two senses, sight and touch, supplies us with the more accurate information as to the position of objects around

us.

The comparison may be made in several ways, one of the most obvious of which is to compare the smallest distances within which two impressions made upon sensitive surfaces can be recognized as separate and distinct. It has been found, for example, that the distance between two luminous points, as two fixed stars, must subtend a visual angle of at least one minute, in order that the sources of light may be recognized as separate and distinct from one another. This angle corresponds to a distance of 0.00438 millimetre on the retina. The smallest distance upon the surface of the body at which two tactile impressions are recognized as distinct is, according to Weber's researches, 11 mm. (upon the tip of the tongue). Hence it should follow that the retina is 251 times more accurate than the most sensitive part of

the surface of the body in localizing impressions made upon it. It may be objected, however, that a comparison of this sort has little value, inasmuch as it is the optical image of the object which is applied to the retina, while the object itself is brought in contact with the surface of the body. It is interesting, therefore, to compare the absolute size of the smallest intervals by which two external objects must be separated in order that they may make distinct impressions upon the two senses. In making the comparison regard must be had to the distances within which both senses can be practically employed. The sense of touch can not be exercised beyond an arm's length, and the sense of sight is useless for objects nearer than the nearest point for which the eye can be accommodated. About thirty inches may be assumed as the longest convenient range of touch, four inches as the shortest of distinct vision. An angle of 1', which has been taken as the minimum visual angle, is subtended at the distance of four and of thirty inches by lines of 0.03 and 0.2 mm. respectively. That is, two points, 0.03 mm. apart, at a distance of four inches from the eye, are seen to be distinct and separate, and the same is true of points 0.2 mm. apart at thirty inches from the eye. Now, since, according to Weber, two points, in order to produce separate impressions upon the skin at the ends of the fingers, must not be less than 2-2 mm. apart, it appears that within the limits of four and thirty inches the sense of sight is from ten to seventy times more accurate than that of touch. In these tests, however, it is only the accuracy and delicacy of two sensitive surfaces that are compared together, but in common life the data of sight and touch are intimately associated with those of muscular sense; and the inquiry needs to be continued to ascertain whether the superiority of vision is maintained under these circumstances. The fact that we depend more upon touch than upon vision in estimating slight differences of level in contiguous surfaces, as when we draw the finger-nail over the line of junction, indicates that this may not always be the case.

The experiments of Drs. Bowditch and Southard had especial reference to the determination of the relative accuracy of sight and touch, when aided by the muscular sense, and were applied for the determination of the precision with which a movement can be executed toward a point, the position of which has been determined by sight or by touch. A small object was put upon a white sheet of paper in different positions. The experimenter, having ascertained its position by sight, shut his eyes and endeavored to touch the object with the point of a pencil held in his right hand. In another set of observations he himself put the object in position with the left hand, having his eyes closed, and then, keeping his eyes closed, endeavored to place the pencil-point upon it as before. In a preliminary series of sixty trials, in half of which the

position of the object was determined by sight, and in the other half by touch, sight appeared to be twice as accurate for the determination as touch. The experiments were then varied in different ways, employing indirect instead of direct vision, to eliminate the aid that might be given by the muscular sense of the muscles that move the eye; by using the same hand to place the object and to search for it; to determine the effects of different intervals of time; and to ascertain the effect of maintaining the head in a fixed position. In all, seven sets, of six hundred experiments each, making in all four thousand two hundred trials, were performed. The result of the whole was, that the most accurate spatial knowledge was obtained by direct vision. The effect of fixing the position of the head was to diminish the accuracy of the localization, but even under those circumstances the errors were, in nearly every instance, less than those met with in the other methods of experimenting. The method next in accuracy was that of localization by touch, with the same hand by which the movement in search of the object was executed, the head being free to move. "It may, at first sight," observe the experimenters, "seem surprising that this method should be less accurate than that of direct vision. It would be reasonable to suppose that the position of an object having been once determined by the sense of touch, it would be possible to place the hand upon it a second time with greater precision than would be possible when the position had been determined by the sense of sight. That the reverse is the case, is probably to be accounted for by the fact that in our daily life all our movements are guided by the sense of sight to a much greater extent than by the sense of touch." Next in order of accuracy of localization came the experiments with indirect vision; next, those in which the position of the object was determined by the same hand with which the movement in search of it was made, but the head was fixed. Least accurate of all the methods employed was that of touch with the opposite hand. The experiments respecting the effects of time showed that a slight interval is required for the formation of a mental image of the object in space, and that this interval is about two seconds, to which point the accuracy of the identifications increased, and after which it diminished. The results of the experiments, having been obtained entirely from one person, are liable to correction for the personal equation; and it is suggested that it would be a very interesting extension of the research, to inquire how far the various occupations of life affect the accuracy of execution of the movements. "It might, perhaps, be expected that the power of the blind to determine the position of objects by the sense of touch would be found, when tested in this way, to be much greater than that of persons possessed of sight. A few preliminary experiments, however, which have al

ready been made, seem to indicate that this is not the case."

M. Ranvier has been much assisted in his investigations of the structure of the organs of touch by the examination of the structure of infants. At birth, the nerves of touch may be found to pass into certain papillæ on the palmar aspect of the fingers, immediately beneath the cells of the mucous layer of Malpighi, where they form a net-work of ramifications which, though distinct, are closely pressed together. No cellular elements are at this time mixed with the net-work, but a small collection of round cells exists beneath it. These gradually surround the net-work and pass in among its branches; the whole soon becomes united, and a tactile corpuscle is formed. Sometimes the corpuscle remains unilobar, but more frequently other lobes are formed in the same manner as the first one, and joined to it. Hence it is that, in young children, the nerve-fibers which enter into the composition of the tactile corpuscles are separated by layers of cells, which, in the course of development, become pushed to the periphery of each lobe, and the most of them undergo a considerable atrophy. This fact suggests that they are not nervous in their nature, for the nerve-cells, so far from undergoing atrophy during growth, gradually increase in size to their full development. M. Ranvier has not perceived any communication between the nerve-fibers and the cells in the tactile corpuscle; the ramifying branches of the nerve-fibers, after a tortuous and usually complicated course, end in free, flattened knobs.

Wolff has examined the mode in which nerves terminate in muscle, and has arrived at the conclusion that the Doyerian eminences, or end-plates, are artificial products. The neurilemma of the nerve passes continuously, he believes, into the sarcolemma of the muscle, and the axis cylinder into the muscle-sub

stance.

The duration of muscular contraction in different muscles of the same animal and in different animals has been made the subject of experiment by Dr. Cash, who has found, in agreement with Weber's previous observations, that some muscles contract under the same stimulus much more rapidly than others, and that temperature exerts a remarkable influence, a diminution of temperature greatly protracting the duration of the two phases of pulsation. He has also shown that the form of the curve presented by each muscle differs from that of others; and that in many instances the tracing is so constant and peculiar as to serve readily to indicate the muscle from which it is derived.

Professor C. M. Woodward, of Washington University, St. Louis, Missouri, has devoted a chapter of his work on the St. Louis Bridge to the review of the affections which the men employed in sinking the piers for the structure suffered from compressed air, and of the theories that were proposed to account for the trouble.

VOL. XXI.-48 A

No serious drawback was perceived to working for four or even six hours consecutively in the air-chamber, till the cutting-edge of the caisson of the east pier was nearly sixty feet below the surface of the river. From that time on it was found best gradually to shorten the working-time and make the rests longer, till the 5th of February, when a depth of sixty-five feet had been reached, and the work-time was made three watches of two hours each, with twohour rests. The first effect noticed upon the men was a muscular paralysis of the lower limbs, without pain, which would pass off in a day or two, but which became more difficult to subdue, more extended and painful, as the caisson was sunk deeper. It was regarded as a subject for joking at first, but grew more serious by the middle of February, after which, the depth being seventy-six feet, severe cases became more frequent. The superintendent of the work noticed the fact that the sick men were often thinly clad and poorly fed. At the end of March, several persons having died within a few days shortly after coming out of the excavations, Dr. A. Jaminet was appointed to take medical charge of the men and establish suitable regulations for their well-being. He had been a frequent visitor to the air-chamber, had noticed the men as they came out, and had observed that their appearance was pallid and cold, that in some the pulse was quick but somewhat weak, while with others it was as low as sixty; that without exception the workmen complained of fatigue; that the pulse always quickened on entering the air-chamber, though it soon fell to the normal rate, and even lower; that the number of respirations increased, and a feeling of exhilaration came on in the air-chamber; and that the workmen sweated profusely during their stay in it, although the temperature was often below 60° Fahr. The air-lock was, as a rule, excessively warm when the pressure was increasing, and excessively cold when the pressure was diminishing. On the day the caisson touched the rock, when the pressure was forty pounds above the normal, Dr. Jaminet was conscious of a great loss of heat and a violent pain in his head, while in the air-lock on his way out, and afterward became partially paralyzed. Among six hundred men employed, one hundred and nineteen cases important enough to need medical treatment were reported at both piers, fourteen of which died and two were crippled. Post-mortem examinations were held in the case of eight. Dr. Clark, of the City Hospital in St. Louis, believed that the congestion observed was caused by the forcing of the blood in upon the interior organs of the body in consequence of the increased atmospheric pressure. Another physician thought the men were poisoned by carbonic acid which had been abnormally retained within the system while in the airchamber, but which was set free as soon as the pressure was removed. Dr. Jaminet thought the affections were due to physical exhaustion