When cane-sugar is given to dogs it is found, either unchanged or converted into sucre interverti or lactic acid, in the whole length of the digestive canal. After it has been given for several days it may be found in the urine, and in the bile, blood, and chyle. When cane-sugar is introduced directly into the blood it passes into the urine; but when the same quantity of sucre interverti or lactic acid, was so introduced none was detected in the urine. In order that cane-sugar may be destroyed in the blood (i. e. ultimately reduced to carbonic acid and water), it must first be transformed into sucre interverti, or lactic acid in the digestive canal. Raw starch is very imperfectly digested by men and carnivora. The greater part of it may be found unaltered in the excrements. A greater effect is produced on it by the digestive organs of herbivorous rodents. It undergoes no change in their stomachs; but in the contents of their small intestines (which are always alkaline, except sometimes at the pyloric part of the duodenum) there are found, together with entire starch granules, others that are cracked, eroded, or almost wholly destroyed; and, also, dextrine with traces of grapesugar. The cæcum contains an acid paste, in which there are some entire starch granules, dextrine, grape-sugar, and lactic acid. The same materials are found in the rectum. The dextrine, grape sugar, and lactic acid may also be detected in the blood and the bile, but not in the urine of these animals; and the blood of their vena portæ contained more water and more of these three substances than their arterial blood did-making it sure that they are absorbed by the blood-vessels, not by the lacteals. Graminivorous birds digest raw starch more completely than mammalia do. It undergoes no change in their crops; and in their gizzards, though there are traces of dextrine and grape-sugar, yet nearly all the starch-granules appear unchanged. In the small intestines the starch-granules are gradually more and more destroyed, and ultimately they undergo the same changes as in the intestines of the herbivorous rodents, but more completely. In both, the authors consider the changes to be due to the high temperature, the alkaline reaction, and the presence of a secreted principle which acts like diastase, only with less energy: all which conditions exist in greater force in the birds than in the mammalia. When the starch-granules have been burst by cooking they are digestible by men and carnivorous animals. Their solution commences in the stomach, and is slowly continued through the intestinal canal. The products are dextrine, grape-sugar, and lactic acid; which are found mixed with some starch remaining unchanged. If more than a certain proportion (one gramme, at the most, for an adult dog) of a feculent or saccharine principle be mingled at once with the blood, sugar is always eliminated by the kidneys. Hence the slow introduction into the blood of the products derived from the digestion of these principles appears to be an essential condition for their due disposal; and this condition is secured by two chief means, namely, the slowness of their solution, and the chief manner of their absorption. They are formed into soluble compounds in the intestines; and these being absorbed by the blood-vessels, are carried to the liver, where, if combustible matters are in excess in the blood, the greater part of them are secreted and discharged with the bile into the intestines, whence some of them may be absorbed with the other soluble constituents of the bile. "Thus then is established a limited circulation of the combustible matter, which, by this admirable artifice, is only gradually carried into the general circulation.” These conclusions concerning the transformations which starch undergoes in digestion are, to some extent, confirmed by Dr. R. D. Thomson,* whose experiments show that dextrine and soluble starch exist in the stomachs of pigs fed on farinaceous food during and for some time after digestion, and Philos. Mag., May 1845; and Lancet, May 17, 1845. that sugar exists in the blood of the same animals in the proportion of from 2:57 to 805 grains in 1000 grains of the serum. In a subsequent memoir MM. Bouchardat and Sandras state that the principle which, as above-mentioned, appears to act like diastase in the transformations of starch is secreted chiefly by the pancreas. They find the pancreatic fluid of birds transparent, viscid, slightly alkaline, and capable of liquefying starch-paste, and of transforming it into dextrine and grape-sugar. Portions of pancreas cleared of blood and large vessels possess the same power in a very high degree; and no other organ besides the pancreas, and in a slighter degree the salivary glands, possesses such a power. It is, moreover, wholly destroyed both in the pancreatic fluid and in the pancreas itself by such influences as destroy the like property in diastase, such as a temperature of 212°, tannin, mineral acids, metallic salts, &c. The same influence which these authors ascribe to the pancreatic secretion is ascribed by M. Mialhe‡ to the saliva, from which he gives directions for obtaining the digestive principle, animal or salivary diastase,--by filtering it and then treating it with five or six times its weight of absolute alcohol. The diastase being insoluble in alcohol is thus precipitated in white flocculi. He describes the aqueous solution of this substance as insipid and neutral, not precipitable by subacetate of lead, and when left to itself undergoing a transformation into butyric or some similar acid. With raw starch this salivary diastase requires several days for the production of dextrine and sugar of starch; but with starchpowder the change is quickly effected; and with starch-paste it is very speedily completed if aided by a temperature of about 160°.§ The experiments of M. Lassaigne || confirm those of MM. Bouchardat and Sandras as to the properties of the pancreas and its fluid; and, at least in great measure, those of M. Mialhe on the properties of the saliva. He shows that at the natural temperature of the body saliva has no effect on whole starch, and that mastication does not change the form in which it naturally exists in cereal grains; that horse's saliva does not act on starch even when its grains are broken; but that human saliva, though it does not affect raw and whole starch at a temperature of 100°, can even at a temperature of from 64° to 68° convert powdered starch partly into dextrine and partly into sugar of starch; the envelopes of the granules preserving at the same time their property of becoming violet when touched with iodine. Influence of the Bile in digestion. Dr. Platner** has made experiments to find how the bile contributes to digestion. He has confirmed, what Simon and others showed, that the fæces contain none of the bile except its colouring matter [and some of its fat?]; and what Purkinje showed, that bile will put a stop to or prevent the artificial digestion of coagulated albumen. On mixing pure artificial digestive fluid, neutralized by carbonate of soda, with bile, no change took place; but on adding hydrochloric acid to the mixture it became very turbid. The same happened when bile was mixed with digestive fluid not neutralized; but hydrochloric acid added to bile alone produced no precipitate. The precipitate consisted of bilic acid united with some organic body, perhaps pepsin, explaining probably the fact quoted above from Purkinje. When bile was added to a solution of albumen in acetic acid, a precipitate * Archives Gén. de Médecine, Mai 1845; Report from the Acad. des Scienees, 14 Avril. + See in connexion with this subject a paper by M. Bouchardat, "Sur la fermentation saccharine ou glucosique," in the Annales de Chimie et de Physique, Mai 1845, t. 89, p. 61. Ibid., 5 Avril 1845; Report for the 31st of March. According to Dr. R. D. Thompson (1. c.) the transformation of starch into dextrine is effected to some extent by boiling it for half an hour in pure distilled water. Arch. Gén. de Médecine, Mai 1845, from the Report of the Acad. des Sciences, 7 Avril. results were opposed to those of M. Mialhe. In the earlier paper his ** Muller's Archiv, 1845, Heft iv. He has since published a special work, "Ueber die Natur und den Nutzen der Galle," Heidelberg, 1845; but I have not yet received it. Another work relating to the physiology of the bile is H. Meckel, De genesi Adipis; Halis. 1845, 8vo. was formed which was insoluble in all acids, but soluble in alkalies. When bile and albumen were mixed and acetic acid added, a precipitate like coagulated fibrine was formed; and a similar precipitate was formed by the agency of even carbonic acid; showing that although the bilate of soda (i. e. the pure principle of bile) retains its composition under the action of either acids or alkalies alone, yet it is decomposed easily by combinations of acids with organic substances. When bile was added to a solution of albumen or gelatine obtained by artificial digestion, precipitates were formed which were soluble in acetic acid and consisted of bilic acid united with the organic substance. Sugar and gum in like circumstances appeared to unite with the fatty matters of the bile. Faces. The usual microscopic constituents of human fæces are thus enumerated by Dr. Gobee. 1. A large quantity of vegetable cellular tissue, with or without epidermis and hairs. 2. Vegetable hairs. 3. Vegetable spiral vessels. 4. Elongated quadrangular plates of light yellow colour in great abundance, of uncertain nature; they are not affected by acetic acid, and are insoluble in cold ether, but iodine displays transverse striæ on them. [Probably they are portions of muscular fibre. I have found such, tinged pale yellow by the bile, in the fluid discharged through an artificial anus.] 5. Large quantities of crystals of phosphate of ammonia and magnesia. 6. Fat-globules or cells in various quantity. 7. A great quantity of granules. 8. Few epithelium- and mucus-cells. 9. Much of the brown-colouring matter of the bile. ABSORPTION. Structure of the Lymphatics. The subject of one of Mr. Goodsir's excellent essayst is the structure of the lymphatic glands. At the points of connexion between the extra- and intra-glandular lymphatic vessels, the coats of the former (whether afferent or efferent) separate. The outer coat is continued into the external capsule of the gland, from which processes pass inwards, binding together the substance of the gland, and supporting the vessels within it. The middle, or fibrous coat, is usually nearly lost, as the vessels pass towards the centre of the gland. But the internal coat becomes thicker and more opaque in the intra-glandular lymphatics; and when, in any of these thickened, dilated, and oft anastomosing vessels, it is broken up, it appears composed of two substances; namely, first, a thin transparent membrane, in which ovoidal bodies, containing one or more minute vesicles, are imbedded, as" germinal spots," at regular distances; and secondly, thick layers of closepacked spherical nucleated particles about 1-5000th of an inch in diameter, which make the vessel appear opaque, and leave only a narrow and irregular canal along its axis, the walls of which canal appear formed by them, not by any membrane lining them. The capillaries in the lymphatic glands ramify in contact with (not in the substance of) the external layer of their coats; as they do on the ultimate ducts of the true secreting glands; and they form as fine a network. The general result of these observations is plainly favorable to the opinion of an intimate analogy between the lymphatic and the true secreting glands ; of which some account was given in the last Report, and more will presently be said in speaking of the glands without ducts. Process of Absorption. Some observations by E. H. Weber§ are said to prove that the chyle is first absorbed into the epithelium-cells covering the villi, which, at a certain period, are found full of chyle-globules, and from which it is transferred into the proper cells of the villi, to be by them conveyed to the lacteal vessels. And among the cells of the villi, it is said that Kliniek; Tijdschrift voor wetensch. Geneeskunde; voor G. C. Gobée, 1844, St. iv. + Anat. and Pathol. Observations, No. viii, p. 44. The expression has reference to the author's general theory of nutrition: the bodies he describes appear to me ideutical in aspect with the nuclei or cytoblasts of many secreting gland-ducts. Archives d'Anat. Gén, et de Physiol., Jan. 1846. two peculiarly large ones are often seen in man during digestion, which touch each other, and of which one contains an opaque-white liquid, and the other a clear fatty matter. Experiments on absorption have been performed by Mr. Fenwick, and their results are very like those obtained by Herbst. 1. He relates two experiments to show that indigo will pass into the lacteals. 2. He relates many to prove that the lacteals do not absorb strychnia, or milk, or other food, from any part of the digestive canal in which the blood is not circulating. 3. He shows, as Herbst does, the passage of liquor sanguinis and blood into the lacteals when the adjacent blood-vessels are much congested. 4. In other experiments, oily matters (?) and prussiate of potash injected into the pleura of a rabbit were shortly after found in the lacteals. 5. Others again show that the action of the lacteals and lymphatics is independent of nervous influence. 6. And others confirm the fact already known, that they continue to propel their contents after apparent death. 7. From his experiments, from analogy, and from many ingenious, but I think insufficient, arguments, Mr. F. concludes that these vessels obtain their fluid neither by absorption, nor by secretion from the blood-vessels adjacent to them, but by parts of the contents of the blood capillaries, according to the degree of congestion, being directly and mechanically effused into them. Propulsion of Lymph. An attempt has been made by Dr. Bidder† to determine the average quantity of lymph and chyle which flow through the thoracic duct in a given time. The measurements were made by collecting what flowed from the thoracic duct immediately after death. In five cats, the fluid continued to flow from one to six minutes, and, judging by the quantity collected in this time, the average quantity which would have flowed in an hour, was 373 grains (the extremes being 276 and 480 grains); and the average proportion between the weight of the cat and the weight of the chyle and lymph, which at the same rate, would have flowed in twenty-four hours, was as 5.34 to 1 (the extreme proportions being as 68: 1, and as 51:1). In two dogs the average rate of efflux (similarly calculated) was 3858 grains in the hour; and the average weight of the dogs was, to that of the chyle and lymph which would have flowed in twenty-four hours, as 6-66:1. Now, the average weight of blood in cats is, to the weight of their bodies, as 1:57; and of dogs, as 1:4-5; hence the quantity of fluid daily traversing the thoracic duct of a cat, is about equal to the whole quantity of blood in it; and the quantity of the same in a dog is equal to two-thirds of its blood. Lymphatic hearts. Volkmann‡ has proved that the rhythmical movements of the lymphatic hearts of frogs depend on the direct influence of portions of the spinal cord. They cease on the instant of destroying the cord, though those of the blood-heart continue for many hours. But repeated experiments showed that the contractions of the anterior hearts would continue long while they retained a nervous connexion with the cord about the third vertebra; and those of the posterior hearts as long, if their connexion with the cord at the eighth vertebra was uninjured. The movements thus continued in the lymphatic hearts though the whole of the cord, except these portions, were destroyed; and on the instant of destroying either of these portions, though all the rest of the cord were intact, the movements of the corresponding hearts ceased. Removal of the brain had no influence. The movements continued also after the division of the posterior spinal roots (they were therefore not reflex), but they ceased directly on the division of the anterior roots. + Muller's Archiv, 1845, Heft i. * Lancet, Jan. 11, 18, 25, Feb. 1, 1845. Ibid. 1844, Heft iv, and Wagner's Handworterbuch, art. Nervenphysiologie, p. 489. Valentin, in the body of his Physiologie (vol. ii, p. 767), denied the truth of these experiments, but in a later appendix confirms them. For other papers on the lymphatics, see Oesterlen, as presently quoted; H. Nasse, an elaborate article on the lymph in Wagner's Handworterbuch; and papers on some unusual arrangements of the lymphatics, by Svitzer and von Patruban, in Muller's Archiv, H. ii, 1845. GLANDS WITHOUT DUCTS. In the last Report I deferred the notice of Dr. Oesterlen's observations* on the vascular glands that I might include with it that of the then unpublished essays of Mr. Simon.† I am thus able to set out more briefly the results of the two most important works ever yet published on these organs, and this with advantage even to Dr. Oesterlen's work, for his facts gain importance and clearness by the corroboration and bright illustration which they receive from the truly admirable researches of Mr. Simon. Thymus Gland. According to Mr. Simon, the earliest condition of the thymus gland is that of a simple tube of transparent homogeneous membrane, with granular and dotted contents. It presents at regular intervals elongated thickenings of its wall, which are probably the attenuated nuclei of a series of primordial cells, by the fusion of which the tube may be first formed. The tube has no connexion with the respiratory mucous membrane. In the next stage the tube (which remains in the axis of each half of the gland as its central cavity,) bulges at certain points of its length, forming diverticula or follicles, which communicate with and have the same structure and contents as itself. These usually assume hemispherical or pedunculated forms; and, in the next stage, themselves branch or form secondary and tertiary bulgings; and this is generally effected without elongation of the isthmus or pedicle by which the primary follicles were connected to the main canal, so that the secondary ones appear sessile. The progress of the development of the gland consists in repetitions of this process-the growth of follicles extends successively to all parts of the main tube; in each new crop of follicles are repeated the same acts of development and branching; and the whole substance of the gland enlarges by interstitial growth. The gland continues growing through the whole "age of early growth;" and the period at which it attains its greatest size cannot be more nearly determined than the age of completed growth of the whole body can. Mr. Simon's observations on this point agree with those of Haugsted. This account of the development, affords some notion of the mature structure of the thymus. According to both Simon and Oesterlen, whose observations now begin to coincide, it consists of a collection of polygonal mutually flattened membranous cells, from half & line to nearly two lines in diameter, the terminal vesicles or follicles of the gland. These are ranged in masses round a common axis; each mass forming a sort of cone, whose apex is directed towards the axis. The vesicles or cells are not completely close and separate, they are closed in about three fourths of their periphery; by the remaining part, each is attached to the general trunk of the glandular substance and opens into some diverticulum of its common cavity. The walls of the vesicles are formed by the same kind of homogeneous membrane as the primitive tube; each having on its exterior a capillary network; groups of them are connected by investing areolar tissue, in which is mingled a small proportion of delicate elastic fibrils. The vesicles are filled by a fluid and a multitude of corpuscles. The corpuscles, according to both observers, have the structure and relations of nuclei. They are generally circular, yet often deviate widely and variously from this form, and are flat and disc-like. Their average diameter is of an inch; they are characteristically dotted, having from two to five very small dark spots, either scattered, or collected into a single corpuscle in their centres. In animals past the most active period of the thymus, there may be found cells in which these dotted corpuscles appear as nuclei, and which are, or become, perfect fat-cells. In his Beitrage zur Physiologie; Jena, 1843, 8vo, pp. 1-95. + A Physiological Essay on the Thymus Gland; London, 1845, 4to; and, The Comparative Anatomy of the Thyroid Gland; in the Philosoph. Transactions, 1844, part 2. |