640 ABSORPTION. 



lobe of Spigelius, towards which they converge. From this point, they 

 penetrate the substance of the liver, through which they ramify with 

 great minuteness, and finally empty themselves into the receptaculum 

 chyli. To prove, that the chyliferous vessels do pass through the liver, 

 he put a ligature around the duct below the diaphragm, in a dog which 

 had eaten largely, and when digestion was in full activity. The chy- 

 liferous vessels were observed to swell, and their whitish colour was 

 distinctly perceived. They could be traced, without much difficulty, 

 from the interior of the intestinal canal, through the mesenteric glands, 

 as far as their entrance into the liver. 



The chyliferous vessels are composed of two coats; the outer of a 

 fibrous and firm character; the inner very thin, epithelial, and gene- 

 rally considered to form, by its duplicatures, valves. These are, of a 

 semilunar form, arranged in pairs, and with the convex side towards 

 the intestine. Their arrangement has appeared to be well adapted for 

 permitting the chyle to flow from the intestine to the thoracic duct, 

 and for preventing its retrograde course ; but M. Magendie 1 affirms, that 

 their existence is by no means constant. These reputed valves are 

 considered by M. Mojon 2 to be true sphincters. By placing the lymph- 

 atic vessels on a glass plate, and opening them through their entire 

 length, he observed by the microscope, that they are formed of circular 

 fibres, which, by diminishing the size of the vessel at different points, 

 give rise to the nodosities observed externally. If the ends of a 

 varicose lymphatic be drawn in a contrary direction, these nodosities 

 disappear, as well as the supposititious valves. Mojon observed, more- 

 over, that the fibrous membrane of the lymphatics has longitudinal, as, 

 well as oblique, filaments passing from one narrow portion to another. 

 The longitudinal fibres have their two extremities attached to the trans- 

 verse fibres, which, according to him, constitute the sphincters or 

 contractors of the lymphatics. He explains the difficulty often ex- 

 perienced in attempting to inject the lymphatic vessels in a direction 

 contrary to the course of the lymph, by the circumstance, that the 

 little pouches formed by the sphincters, and the relaxation or disten- 

 sion of their parietes on filling them with injected matter, diminish the 

 calibre of the tube, and can even close it entirely. The smallest lacteals 

 appear to be destitute of valves; but valves are perceptible in those of 

 less than one-third of a line in diameter, and they have the same 

 structure as those of the veins. The minute lacteals in the villi are 

 said to consist of a single membrane with elongated cell-nuclei, corre- 

 sponding to the longitudinal fibrous membrane of the veins, but not lined 

 by epithelium. Some anatomists describe an external coat, formed of 

 condensed areolar tissue, which unites the chyliferous vessels to the 

 neighbouring parts. 



The mesenteric glands or ganglions are small, irregularly lenticular 

 organs; varying in size from the sixth of an inch to an inch; nearly 

 one hundred in number, and situate between the two laminae of the 

 mesentery. In them, the lymphatic vessels of the abdomen termi- 



1 Precis Elementaire, 2de edit., i?. 177, Paris, 1825. 



2 Op. citat. and Arner. Journal, &c., for Aug. 1834, p. 465. 



