PART FOURTH. Chronicle of Medical Science (CHIEFLY FOREIGN AND CONTEMPORARY). HALF-YEARLY REPORT ON PHYSIOLOGY. I. CIRCULATION AND RESPIRATION. 1. J. SACHS: An Inquiry into the Seat of the Formation of Carbonic Acid in the Animal Body. (Reichert and Dubois-Reymond's Archiv, 1863, pp. 345.) 2. SCZELKOW: On the Interchange of Gases which takes place in the different Organs of the Body. (Sitzungsberichte der Wien Akad., Band xlv. 1862, p. 171.) 3. M. EDENHUIZEN: Essay on the Physiology of the Skin. Pfeuffer, Zeitschrift, iii. Reihe, Band xvii. p. 35-105.) (Henle and 1. Sachs observes that three opinions may be held upon the seat of the formation of carbonic acid in the animal body: 1. That it is formed in the tissues, from whence it passes into the blood; 2. That it is exclusively formed in the blood; and 3. That it is generated in both places. At first sight the objection made by Ludwig against the formation of carbonic acid in the tissues appears to be a strong one-viz., that if this be the case, the pressure or tension of the carbonic acid in the tissues should be greater than it is in the blood; but direct observations prove the contrary. Thus Schumowsky has shown that even the muscular tissue does not contain more than about 144 per cent. of carbonic acid; and as regards the fluids of the body, Schöffer states the amount of carbonic acid in the urine to be 44 per cent., whilst its proportion in the milk varies, according to Setschenow, from 5:01 to 672 per cent. In all these instances, therefore, it is present in a proportion far below that in which it is contained in the blood. But the force of the objection vanishes if it be remembered that a large portion of the carbonic acid naturally present in the blood is in combination with the phosphate of soda, and that only a small part is really free. In order to ascertain whether carbonic acid is generated in the blood, the method pursued by Sachs was to divide a freshly drawn portion of blood into two parts-to examine the gases in one immediately, and to set the other aside for some hours before obtaining the gases from it. He draws the following conclusions from six experiments, made with great care:-1. The gases contained in the blood after its removal from the body, at ordinary temperatures undergo marked changes in their relative proportions, the oxygen gradually disappearing, and carbonic acid taking its place; the quantity of carbonic acid generated being, however, always greater than the volume of oxygen which has disappeared. 2. The quantity of carbonic acid that is chemically combined in the blood increases with the interval at which it is examined after removal from the body; and he agrees with Schöffer and Sczelkow in consider ing the quantity of chemically combined carbonic acid to be always greater in venous than in arterial blood. 3. Though the number of experiments was too small to found positive statements upon, it appears that after forty-eight hours the quantity of oxygen remaining in the blood is reduced to a mere trace, and after that period (for some time at least) the gases suffer no further change. 4. He was unable to draw any definite conclusions in reference to alterations in the proportion of nitrogen. 5. The presence of fibrin is a necessary condition for the formation of carbonic acid in the blood, but the exact role which it plays cannot as yet be definitely stated. From these results he believes that he is justified in the general conclusion, that carbonic acid is constantly being generated in the blood at the expense of the oxygen present in it, and that consequently carbonic acid is not formed exclusively in the tissues. 2. In Sczelkow's experiments three kinds of blood were compared:-1. That obtained from the carotid artery. 2. That obtained from the femoral vein when the muscles of the leg were quiescent. 3. That obtained from the same vein when the muscles of the leg were tetanized. In the following table the first is indicated by A, the second by V R, and the third by V B: It thus appears that 100 vol. of venous blood returning from muscles at rest contains on the average 6.71 vol. more carbonic acid than is contained in 100 vol. of arterial blood, whilst 100 vol. of venous blood returning from contracting muscles contain 10.79 vol. more CO2 than 100 vol. of arterial blood. On the contrary, the venous blood of quiescent muscles contains 9 per cent. less oxygen than arterial, whilst in the venous blood of contracting muscle the quantity of oxygen may not exceed 1 or 2 per cent., arterial blood containing from 12 to 17.3 per cent. by volume of that gas. 3. Edenhuizen has investigated anew the effects of suppressing the action of the skin in various animals by covering them with different kinds of varnish. The experiments were made upon sheep and rabbits, a dog, a weasel, a mouse, a pigeon, and two frogs. On completely covering the animal, the duration of life was usually longer in proportion to its size, providing it was strong and healthy. If more than from one-eighth to one-sixth of the body were covered in rabbits, they quickly died. Immediately after the operation, a temporary increase in the frequency of the respiratory acts, of the pulsations of the heart, and of the temperature of the body was usually noticed; but in a short time these all fell below the normal standard-at first rapidly, and subsequently more slowly, though uninterruptedly, till death supervened. Other symptoms which appeared when a considerable portion of the skin was varnished were, restlessness, strong rigors, dyspnea, paralysis, tonic and clonic convulsions, languor, and the secretion of a considerable quantity of albuminous urine. On keeping a small part of the skin permanently varnished, it became red, and suppuration occurred in the whole thickness of the corium, whilst in the interstices of the areolar tissue numerous crystals of the triple phosphate of ammonia and magnesia were contained. Similar crystals were found after death in the peritoneal cavity of animals that had died from the application of an entire coating of varnish. Hence it seems probable that ammonia is eliminated by the skin, and experiments made with hematoxylon-paper showed that, under normal conditions, there is an escape of volatile alkali. It is the prevention of the excretion of the ammonia that occasions, according to Edenhuizen, the morbid appearances seen in animals thus killed-viz., congestion of the brain, lungs, liver, spleen, and kidneys; effusion into the pleura, peritoneum, pericardium, and the subcutaneous areolar tissue; and lastly, the ecchymoses so frequently seen in the mucous membrane of the stomach. II. LYMPH, CHYLE, AND BLOOD. 1. C. LUDWIG: On the Origin of the Lymph. (Medizin Jahrbüch., v. A. Duchek and A. Schauenstein, Wien. 1863. Heft iv. pp. 35-72). 2. H. SCOUTETTEN: Recent Experiments made with the view of establishing the Electricity of the Blood, and of Measuring its Electromotor Force. (Gazette Hebdomadaire, tom. ix. 1863, p. 769.) 1. In this memoir the essential results of the investigations undertaken by C. Ludwig, and his friends Herren Noll, Krause, Schwanda, and Tomsa, are given. Ludwig remarks that the considerable pressure under which the lymph is constantly flowing, together with the sudden variations which are observed in the rapidity of the current, are circumstances opposed to the ordinarily-received notion, that it proceeds from the osmosis of the surplus material which has been effused from the blood vessels for the nutrition of the tissues; and that although it has been customary to attribute the movement in part, also, to the pressure of the blood, yet that it is difficult to understand how this force can act if we admit with most writers on the subject three sets of spaces or cavities-namely, one belonging to the bloodvessels, a second formed by the lacunar spaces intervening between the fibres of the connective tissue in the different organs, and a third represented by the cavity of the lymphatic vessels-for it is inexplicable that the fluid effused from the blood should enter the closed system of the lymphatic system rather than percolate through the splits and fissures of the areolar tissue. The researches of Noll, based on these considerations, led him to give a different interpretation of the mode of origin of the lympathic vessels to that usually accepted; and he believes that he can show by injections forced through those vessels in a retrograde direction, that they actually commence, not by closed free extremities, nor by loops, nor by a plexus, but in the interspaces of the connective tissue itself, and that, consequently, the bloodvessels may be regarded as in reality distributed in the interior of the lympathic system, and the fluids effused from the blood, as entering directly the rootlets of the absorbent vessels. In order to render the finest lymphatics of any part visible, Ludwig recommends that the chief lymph-vessels should be exposed and tied during life. On killing the animal a few hours later, the most minute branches, now turgid with fluid, are discoverable, and may readily be injected, though great care and gentleness in the operation are required. The testicles are well adapted for experiments of this nature, since there is no intervening material between the tubuli seminiferi and the blood vessels besides the fibrillar connective tissue; and it can there be readily shown that the lacunar spaces, splits, and fissures of that tissue open into more definite channels lying be tween the several layers of membrane which form the septa of adjacent lobuli; these again, by their union, begin to form sinuous vessels, whose walls are, however, still formed by a condensation of the connective tissue alone. Ultimately these become perfectly defined and cylindrical, with proper walls, and, on reaching the surface of the organ, are provided with valves, and attach themselves to the blood vessels which they accompany in their farther course. He compares the arrangement of the channels in the tunica albuginea and septa to that produced by making a series of openings through a quire of paper, and then shifting some of the leaves, by which means passages are formed that, after running in a straight course through two or three pages, terminate, as it were, in the split between two adjoining sheets, which again open at numerous points into other passages running in the former direction. On injecting fluids into the lymphatics of the testis it may clearly be seen to penetrate between the bloodvessels, the tubuli seminiferi, and the fibrils of the connective tissues, so that these constituents of the gland are on all sides surrounded by the fluid. This account, therefore, closely coincides with that given by His and Brücke of the origin of the lymphatics in the intestinal canal, substituting only the tubuli seminiferi for the Lieberkühnian follicles. Similar investigations upon the kidney and on the cornea led to the same conclusions. In reference to the movement of the fluid in the lymphatics, he remarks that if any hypothesis on the subject be admissible, we must probably attribute it to the difference in the pressure of the blood contained in the blood vessels as compared with the fluid (lymph) contained in the lymph spaces. The testicle is again, on account of the simplicity of its vascular and lymphatic systems and the slight operation required to expose the vessels, admirably adapted to show the effects of artificial variation of pressure in the veins on the amount of lymph produced. Tomsa's experiments on this point showed that the application of moderate pressure to the veins of the plexus pampiniformis was followed by an increased discharge of lymph; in three instances, amounting on the average to 59 per cent., on increasing the pressure, it rose in five animals from 30-1000 per cent., and on the average 370 per cent.-that is, that 37 times more lymph flowed than before. If, however, the pressure was increased till the current of blood was altogether stopped in the veins, the lymph first became bloody, and the flow then altogether ceased. The effects of active congestion, produced by section of the sympathetic nerve, were observed in the neck; and it appeared that though, in some instances, the amount of lymph discharged by the large lymphatic vessels was considerably increased, in others but little effect was perceptible. Other modes of inducing congestion of various parts, as by applying cantharides, produced no remarkable increase in the flow of lymph. It was found that; on diminishing the pressure of the fluids in the lacunar spaces of the connective tissue, as by firm but intermittent pressure of the head and face of a dog with the hands, and stroking the tissues so as to evacute the lymph, much more fluid was discharged; whilst by adopting means that increased the pressure in those spaces less was obtained. As regards the influence of the nerves, it has been shown by Krause that irritation of the portio dura caused an increased flow of lymph from the lymphatics of the face; and the same result was obtained by Schwanda on irritating the interior of the mouth till pain was produced. In similar experiments, to determine the influence exerted by the nerves upon the flow of lymph through the testicles, it was found by Tomsa that irritation of these nerves produced no increase. The difference between these results and those obtained by Krause, are, no doubt, attributable to the double action of the muscles and the valves in the experiments of the latter observer upon the lymphatics of the face. Various facts tend to show that the lymph may be regarded as essentially a filtrate from the blood: for, in the first place, the proportion of albumen in it is considerably less than in the blood, which is in accordance with the known difficulty of albuminous fluids to traverse animal membranes; and again, the proportion of albumen diminishes with increasing temperature, and increases with increasing pressure; and it is remarkable that the effused fluid more closely approximates to the circulating when the pressure is steady and continuous, than when variable and intermittent. Moreover, Tomsa's experiments showed that, by injections of serum at the ordinary pressure of the blood after death, through the blood vessels, a filtrate is discharged from the lymphatics with about the same rapidity as it flows naturally. The serum used in Tomsa's experiments contained from 6.77 to 6.26 of solid residue, that obtained from the lymph-vessels 6:12 to 4-86 parts in 100, therefore, from 1.90 to 0.65 per cent. less; and this is about the percentage residue of ordinary lymph. The rapidity with which the pressure of the blood in the bloodvessels reattains its ordinary height after venesection, is due, according to Ludwig, to the ready communication which exists between the blood vessels and lymphatics, the fluids from the latter immediately re-entering the cavity of the vascular system when the pressure in the latter falls below that of the fluids contained in the lymphatic system. 2. In Scoutetten's experiments, a large, wide-mouthed porcelain vessel was half filled with venous blood; into this a porous vessel was introduced, containing arterial blood. Another small vessel, containing a saturated and neutral solution of sulphate of zinc, was immersed in each kind of blood, and into these solutions two electrodes, made of amalgamated zinc, and connected with a galvanometer, were plunged. The needle of the galvanometer, on the completion of the current, was powerfully deflected, and remained for nearly an hour at the 66th degree. In another experiment, it was shown that arterial blood is positive in relation to venous. And in a third, it was ascertained that the electromotive force generated by the contact of the two kinds of blood might be represented by 1.82, if 58 represented that of a Daniell's cell-i.e., 100 being the electromotive power of pure zinc. III. NERVOUS SYSTEM. 1. GLUGE and THIERNESSE, MM.: Experiments on the Reunion of Sensory with Motor Nerve fibres. (Bulletin de l'Academie Royale de Belgique, vol. xvi. ser. ii. No. 7, 1863, p. 65.) 2. SETSCHENOW, J.: Physiological Investigations upon the Mechanism in the Brain of the Frog for exerting an Inhibitory Influence upon the Reflex Activity of the Spinal Cord. (Pamphlet, Berlin, 1863, pp. 49.) 3. VALENTIN, G.: Upon the Development of Heat during Nervous Action. (Virchow's Archiv, Band xxviii. 1863, p. 1.) 4. R. VIGOUROUX: On the Influence of Respiratory or other Violent Movements of the Body on the Motions of the Iris. (Gaz. Medicale, 1863, p. 664.) 5. V. KEMPEN and THIERNESSE: Upon the Functions of the Roots of the Nervi Vagi and Accessorii. (Bulletin de l'Academie Royale de Med. de Belgique, 1863, tom. vi. p. 184.) 1. The experiments of MM. Gluge and Thiernesse were made to determine whether the functions of nerves are inherent in themselves, or whether the effects produced depend exclusively upon the nerve-centres from which they spring, and the structures to which they are distributed. Their former experiments led them to admit the first alternative-viz., that a sensory fibre could only convey impressions centripetally, and a motor one centrifugally, and that consequently it would be impossible to convert a sensory into a motor fibre. MM. Phillipeaux and Vulpian* found, on the contrary, in their experiments, * C. Rend., January, 1863. |