and of the carnivora, than in that of the herbivora. Mr. Gulliver1 has, however, affirmed, that the colour is due to an immense multitude of minute particles, which he regards as forming the matrix or molecular base of the chyle. These are generally spherical and extremely small,their diameter being estimated at from both to both of an inch. They are of a fatty nature, and their number appears to be dependent upon the amount of fatty matter in the food. Their fatty nature is shown by their solubility in ether, and, when the ether evaporates, by their forming drops of oil. As, however, they do not run together, it has been suggested, that each molecule consists of oil coated with albumen, a view which is supported by the fact, that when water or dilute acetic acid is added to chyle, many of the molecules are lost sight of, and oil drops appear in their place; as if the envelopes of the molecules had been dissolved, and their oily contents had run together.2 The chemical character of the chyle of animals has been examined by Emmert, Vauquelin, Marcet, Prout," Simon,' and Nasse; and is found to resemble greatly that of the blood. In a few minutes after its removal from the thoracic duct it becomes solid; and, after a time, separates, like the blood, into two parts; a coagulum, and a liquid. The coagulum is an opaque white substance; of a slightly pink hue; insoluble in water; but readily soluble in the alkalies, and alkaline carbonates. M. Vauquelin regards it as fibrin in an imperfect state, or as intermediate between that principle and albumen; but M. Brande' thinks it more closely allied to the caseous matter of milk than to fibrin. The analyses of Drs. Marcet and Prout agree, for the most part, with that of M. Vauquelin. The existence of fibrin in it can scarcely be doubted. Like blood, again, chyle often remains for a long time in its vessels without coagulating, but coagulates rapidly on being removed from them.10 Dr. Prout has detailed the changes, which the chyle experiences in its passage along the chyliferous apparatus. In each successive stage, its resemblance to blood was found to be increased. Another point of analogy with blood is the fact, observed by Mr. Bauer,"1and subsequently by MM. Prévost and Dumas, 22 and others, that the chyle, when examined by the microscope, contains globules; differing from those of the blood in their being of a smaller size, the average being 'th of an inch, and devoid of colouring matter. The nature and source of these globules, as well as of those of the lymph which resemble them in all respects, is not determined. They have been supposed to be the nuclei or primordial cells from which all the tissues originate, and to be the source. of the blood globule. 1 Gerber's General Anatomy, by Gulliver, Appendix, p. 88, London, 1842. 2 Kirkes and Paget, Manual of Physiology, Amer. edit., p. 207, Philad., 1849. 3 Annales de Chimie, tom. Ixxx. p. 81. 4 Ibid., lxxx. 113; and Annals of Philosophy, ii. 220. 5 Medico-Chirurg. Transactions, vol. vi. 618, London, 1815. 6 Thomson's Annals of Philosophy, xiii. 121, and 263. 7 Animal Chemistry, Sydenham Soc. edit., p. 354, London, 1845, or Amer. edit., Philad., 1846. 8 Wagner's Handwörterbuch, u. s. w., i. 235, art. Chyle; and Simon, op. cit. 9 Phil. Transact. for 1812. 10 Bouisson, Gazette Médicale de Paris, 1844. 12 Biblioth. Universelle de Genève, p. 221, Juillet, 1821. 11 Sir E. Home, op. cit., iii. 25. Although chyle has essentially the same constituents, whatever may be the food taken, and separates equally into a clot and serous portion, the character of the aliment may have an effect upon the relative quantity of those constituents, and thus exert an influence on its composition. That it scarcely ever contains adventitious substances will be seen hereafter; but it is obvious, that if an animal be fed on diet contrary to its nature, the due proportion of perfect chyle may not be formed; and that, in the same way, different alimentary articles may be very differently adapted for its formation. MM. Leuret and Lassaigne,' indeed, affirm, that in their experiments they found the chyle differ more according to the nature of the food than to the animal cies; but that, contrary to their expectation, the quantity of fibrin in it bore no relation to the more or less nitrogenized character of the aliment. They assign it, as constituents, fibrin, albumen, fatty matter, soda, chloride of sodium, and phosphate of lime. spe Messrs. Tiedemann and Gmelin have communicated the following data in regard to the influence of diet on the chyle. The experiments were made on dogs, and the chyle was taken from the thoracic duct. First. After taking cheese, the chyle coagulated slightly. The clot was little more than a pale red transparent film, and the serum slightly milky. It contained water, 950-3; clot, 1·71: residue of serum, 48.0. Secondly. After the use of starch, the chyle was of a pale yellowishwhite colour, and coagulated rapidly. It contained water 9300; clot and residue of serum, 70.0. The clot was of pale red colour. Thirdly. After taking flesh, and bread and milk, it was of a reddish-white colour, and coagulated rapidly, the clot being of a pale red tint, and the serum very milky. It consisted of water, 915.3; clot, 27; residue of serum, 83.8. Fourthly. After the use of milk it presented a milky appearance, and the clot was transparent, and of a pale red colour. Fifthly. After bread and milk, it contained water, 9611; clot 1·9; residue of serum, 37.0. Sixthly. After flesh, bread, and milk, it was of a yellowish red colour; coagulated firmly, separating into a bright red clot, and turbid yellow serum; and contained water, 933-5; clot, 5-6; residue of serum, 60.9.2 The chief object of Dr. Marcet's experiments was to compare the chyle from vegetable, with that from animal food, in the same animal. The experiments made on dogs led him to the following results. The specific gravity of the serous portion is from 1.012 to 1.021, whether it be formed from animal or vegetable diet. Vegetable chyle, when subjected to analysis, furnishes three times more carbon than animal chyle. The latter is highly disposed to become putrid; and this change generally commences in three or four days; whilst vegetable chyle may be kept for several weeks, and even months, without being putrid.3 Putrefaction attacks rather the coagulum of the chyle than its serous portion. The chyle from animal food is always milky; and, if kept at rest, an unctuous matter separates from it, similar to cream, which swims on the surface. The coagulum is opaque, and has a rosy tint. On the 1 Recherches sur la Digestion, Paris, 1825. 2 Simon, op. cit., p. 358. 3 M. Thénard has properly remarked, that the difference in the time of putrefaction of these two substances, appears very extraordinary. It is, indeed, inexplicable. Traité de Chimie Elémentaire, &c., 5ème édit., Paris, 1827. other hand, chyle from vegetable food is almost always transparent, or nearly so, like ordinary serum. Its coagulum is nearly colourless, and resembles an oyster; and its surface is not covered with the substance analogous to cream. M. Magendie,' too, remarks, that the proportion of the three substances, into which chyle separates when left at rest;namely, the fatty substance on the surface, the clot, and the serum, varies greatly according to the nature of the food;-that the chyle, proceeding from sugar, for example, has very little fibrin; whilst that from flesh has more; and that the fatty matter is extremely abundant when the food contains fat or oil; whilst scarcely any is found if the food contains no oleaginous matter. Lastly:-the attention of Dr. Prout has been directed to the same comparison. He found, on the whole, less difference between the two kinds of chyle than had been noticed by Dr. Marcet. In his experiments, the serum of chyle was rendered turbid by heat, and a few flakes of albumen were deposited; but, when boiled, after admixture with acetic acid, a copious precipitation ensued. To this substance, which thus differs slightly from albumen, Dr. Prout gave the inexpressive name of incipient albumen. The following is a comparative analysis, by him, of the chyle of two dogs, one of which was fed on animal, and the other on vegetable substances. The quantity of pure albumen, it will be observed, was much less in the latter case. The difference between the chyle from food of such opposite character, as indicated by these experiments, is insignificant, and indicative of the great uniformity in the action of the agents of absorption. Researches by Messrs. Macaire and Marcet,3 tend, indeed, to establish the fact, that both the chyle and the blood of herbivorous and carnivorous quadrupeds are identical in their composition, in as far, at least, as regards their ultimate analysis. They found the same proportion of nitrogen in it, whatever kind of food the animal consumed habitually; and this was the case with the blood, whether of the carnivora or herbivora; but it contained more nitrogen than the chyle. These results are not so singular, now that we know that the animal and vegetable compounds of protein are almost identical in composition. (See page 545.) All the investigations into the nature of the chyle exhibit the inaccuracy of the view of Roose, that chyle and milk are identical. 1 Op. citat., p. 174. 4 2 Annals of Philosophy, xiii. 22, and Bridgewater Treatise, Amer. edit., p. 272, Philad., 1834. 3 Mémoir. de la Société de Physique et de l'Histoire Naturelle de Genève, v. 389. ♦ Weber's Hildebrandt's Handbuch der Anatomie, i. 102, Braunschweig, 1830. With regard to the precise quantity of chyle, formed after a meal, we know nothing definite. When digestion is not going on, there can of course be none formed except from the digestion of the secretions of the digestive tube itself; and, after an abstinence of twenty-four hours, the contents of the thoracic duct are chiefly lymph. During digestion, the quantity of chyle formed will bear some relation to the amount of food taken, the nutritive qualities of the food, and the digestive powers of the individual. M. Magendie,' from an experiment made on a dog, estimated, that at least half an ounce was conveyed into the mass of blood, in that animal, in five minutes: and the flow was kept up, but much more slowly, as long as the formation of chyle continued. In experiments on a cat, Professor F. Bidder' found the amount that passed through the thoracic duct in the twenty-four hours, to be in proportion to the weight of the body as 1 to 5.34; or about that which-as elsewhere shown the mass of blood has been generally conceived to bear to the weight of the body. In dogs, the proportion was as 1 to 6.66. It is difficult, however, to establish an average amount where so many elements have to enter into the calculation and so much variation must occur, according to the greater or less amount of aliment taken and numerous other circumstances;3 but that so large a quantity passes as is stated by these observers, almost exceeds belief. 3. PHYSIOLOGY OF CHYLOSIS. The facts referred to,-regarding the anatomical arrangement of the chyliferous radicles and mesenteric glands,-will sufficiently account for the obscurity of our views on many points of chylosis. The difficulty in detecting the extremities of the chyliferous radicles has been the source of different hypotheses; and, according as the view of open mouths or of spongy gelatinous tissue has been embraced, the chyle has been supposed to enter immediately into the vessels, or to be received through the medium of this tissue; or, again, to pass through the parietes of the vessels by imbibition. Let it be borne in mind, however, that the action of absorption is seen only by the "mind's eye;" and that chyle does not seem to exist any where but in the chyliferous vessels. In the small intestine, we see a chymous mass, possessing all the properties we have described, but containing nothing resembling true chyle; whilst, in the smallest lacteal that can be detected, it always possesses the same essential properties. Between this imperceptible portion of the vessel, then, and its commencement,-including the latter, the elaboration must have been effected. MM. Leuret and Lassaigne, indeed, affirm, that they have detected chyle in the chymous mass within the intestine, by the aid of the microscope. They state, that globules appeared in it similar to those that are contained in chyle, and that their dissemination amongst so many foreign matters alone prevents their union in perceptible fibrils. These globules they regard 1 Op. citat., ii. 183. 2 Muller's Archiv. für Anat., s. 46, Berlin, 1845. 3 Prof. Th. L. W. Bischoff, Muller's Archiv., s. 125, Berlin, 1846. 4 Recherches Physiologiques et Chimiques, pour servir à l'Histoire de la Digestion, p. 60, Paris, 1825. as true chyle, for the reason, that they observed similar globules in artificial digestions; and, on the other hand, never detected them in the digestive secretions. In their view, consequently, chyliferous absorption is confined to the separation of chyle, ready formed in the intestine, from the excrementitious matters united with it. But we must have stronger evidence to set aside the overwhelming testimony in favour of an action of selection and elaboration by the absorbents of all organized bodies-vegetable as well as animal. The nutriment of the vegetable may exist in the soil and the air around it; but it is subjected to a vital agency the moment it is laid hold of, and is decomposed to be again combined to form sap. A like action is doubtless exerted by the chyliferous radicles; and hence all the modes of explaining this part of the function, under the supposition of their being passive, mechanical tubes, are inadequate. Boerhaave2 affirmed, that the peristaltic motion of the intestines has a considerable influence in forcing chyle into the mouths of the chyliferous vessels; whilst Dr. Young3 is disposed to ascribe the whole effect to capillary attraction; and he cites the lachrymal duct as an analogous case, the contents of which, he conceives,— and we think with propriety,-are entirely propelled in this manner. The objections to these views, as regards the chyliferous vessels, are sufficiently obvious. The chyle must, according to them, exist in the intestines; and, if that of Boerhaave were correct, we ought to be able to obtain it from the chyme by pressure. As the chyle is not present, ready formed, in the intestine, the explanations by imbibition and by capillary attraction are equally inadmissible. There is no analogy between the cases of the lachrymal duct and the chyliferous vessels; even if it were admitted, that the latter have open mouths, which is not the case. In another part of this work, it was affirmed, that the passage of the tears through the puncta lachrymalia, and along the lachrymal ducts, is one of the few cases in which capillary attraction can be invoked, with propriety, for the explanation of functions executed by the human frame. In that case there is no conversion of the fluid. It is the same on the conjunctiva as in the duct; but, in the case of the chyliferous vessels, a new fluid is formed: there must, therefore, have been an action of selection exerted; and this very action would be the means of the entrance of the new fluid into the mouths of the lacteals. If, therefore, we admit, in any form, the doctrine of capillary tubes, it can only be, when taken in conjunction with that of the elaborating agency. "As far as we are able to judge,' says Dr. Bostock, "when particles, possessed of the same physical properties, are presented to their mouths (the lacteals), some are taken up, while others are rejected; and if this be the case, we must conceive, in the first place, that a specific attraction exists between the vessel and the particles, and that a certain vital action must, at the same time, be exercised by the vessel connected with, or depending 1 F. Arnold, Lehrbuch der Physiologie des Menschen, Zürich, 1836-7; noticed in Brit. and For. Med. Review, Oct., 1839, p. 479. 2 Prælect. Academ. in Prop. Instit. Rei Med., § 103. 3 Medical Literature, p. 42, Lond., 1813. 4 Physiology, edit, cit., 622, Lond., 1836. |
