426 OF NUTRITION. 



progress along the Lacteals. No source for this nitrogen can be suggested 

 except the Blood: and the influence of the blood upon the contents of the 

 absorbent vessels, must be in part communicated through the vasa vasorum 

 distributed upon their walls, (since in the cold-blooded Vertebrata there are no 

 lymphatic glands,) but chiefly in the Lymphatic Glands, where the blood-ves- 

 sels and absorbents come into extremely close relation. The idea that the 

 Blood is deprived, in the Mesenteric vessels, of fcome of its azote, seems to 

 derive important confirmation from the fact, that the secretion of the Liver, 

 which is chiefly formed from blood that has returned from these vessels, con- 

 sists almost entirely of unazotized ingredients (Chap. xn.). It may be con- 

 ceived, then, that whilst the Albuminous matter originally present in the Chyle 

 is being converted into Fibrin, new Albumen is being formed at* the expense of 

 the Fatty matter. The same account is applicable to the Lymphatics, a part of 

 whose functions it is, to bring the oily matter stored up in the Adipose tissue 

 within the sphere of the nutritive operations ( 468) ; and the variation in the 

 circumstances which may render this necessary, fully accounts for the varia- 

 tion in the amount of Oily and Albuminous matter presenting itself in this 

 fluid. It must be acknowledged, however, that the views here offered are in 

 great part hypothetical. They derive some confirmation, however, from the 

 circumstance recently pointed out by Mr. G. Ross,* -that the constituents of 

 fatty matter, added to those of uric acid, would very nearly give the atomic 

 constituents of albumen; whence it might be surmised that, when there is a 

 demand for Protein-compounds in the system, azotized matter, which would 

 otherwise be excreted, may be united with non-azotized compounds taken in 

 as food, in order to supply its wants. The fact, which constitutes an important 

 feature in the Physiology of Secretion ( 648), that a separation of Protein- 

 compounds into two such classes of bodies is continually taking place in the 

 living economy, would seem to render the possibility of their union greater. 

 An important source of fallacy, however, attends all deductions founded upon 

 the differences observed in the Chyle in the several parts of its course through 

 the Lacteals; viz., that we cannot be at all sure how far this is dependent upon 

 an actual interchange of ingredients with the Blood, taking place by Imbibition 

 or Endosmose through the very thin parietes of the contiguous vessels. The 

 whole question offers a very wide scope for further inquiry. 



568. The fluid drawn from the Thoracic Duct, and from the Absorbent ves- 

 sels which empty their contents into it, is frequently observed to present a 

 decided red tinge, which increases on exposure to the air. This tinge is due 

 to the presence of true Blood-corpuscles ; but these are somewhat modified in 

 form and size, being a little smaller than the ordinary Blood-discs, and fre- 

 quently angular, granulated, or indented at the edges. By Mr. Lanet it is 

 stated that this intermixture is accidental ; and that it results from the absorp- 

 tion of Blood-particles into the Lymphatics, at the points where the latter are 

 divided, in making the sections necessary to expose the centres of the Absorbent 

 system : and he mentions a striking fact in illustration of his view. He con- 

 siders that the alteration in the character of the corpuscles is due to the action 

 of the Chyle on the Blood, since many other fluids will produce analogous 

 effects ; and he states that shortly after a flow of chyle into the blood, a large 

 number of such altered discs may be seen in the circulating fluid. On the 

 other hand, Mr. Gulliver and several eminent observers, regard these blood- 

 discs as true constituents of the fluid of the absorbents ; and suppose that they 

 are in process of formation. Reasons will hereafter be given, however, for 

 the belief that the red Blood-discs are not formed from the Chyle-corpuscles ; 



* Lancet, 1842-3, vol. i. 



f Cyclopaedia of Anatomy and Physiology, vol. iii. p. 220. 



