650 ABSORPTION. 



ceases; the lacteals empty themselves, and the villi become flaccid. 

 During the interval of repose, the epithelium is renewed for the protec- 

 tion of the surface of the villi, and for the secretion function of the 

 follicles of Lieberkuhn. It is considered by Mr. Goodsir, that the 

 epithelium cells have their origin in certain nuclei, which he has de- 

 tected scattered through the basement membrane. 



These views were embraced by Dr. Carpenter; but they are by no 

 means established. It is denied, indeed, by Reichert, 1 from his own and 

 Bidder's observations, that the epithelium is ever so shed from the diges- 

 tive canal, in or after any act of digestion, as to leave any portion of 

 the subjacent mucous membrane uncovered or raw ; and Prof. E. H. 

 Weber 2 distinctly observed the chyliferous vessels filled with chyle, 

 although the mucous membrane was covered with epithelium. The 

 materials of the chyle, therefore, to enter the vessels must have passed 

 through the epithelium. During absorption, he noticed the prismatic 

 cells of the cylinder epithelium experiencing change of form and colour, 

 and in rabbits and frogs becoming tumid, and containing chyle cor- 

 puscles. In man, beneath the epithelium is a second layer of cells, 

 which are neither conical, cylindrical, nor prismatic, but round; many 

 of which are filled with an opaque white ; and others with a transparent, 

 oleaginous fluid; so that different cells appeared to absorb different 

 fluids. 



It has already been said, that chyle always possesses the same 

 essential properties; that it may vary slightly according to the food, 

 and the digestive powers of the individual; but rarely if ever contains 

 any adventitious substance, the function of the chyliferous vessels 

 being restricted to the formation of chyle. The facts and arguments, 

 in favour of this view of the subject, will be given hereafter. 



The course of the chyle is, as we have described, along the chylife- 

 rous vessels, and through the mesenteric glands into the receptaculum. 

 chyli or commencement of the thoracic duct ; along which it passes into 

 the subclavian vein. The chief causes of its progression are, first of 

 all, the inappreciable action, by which the chyliferous vessels form and 

 receive the chyle into them. This formation being continuous, the 

 fresh portions must propel those already in the vessels towards the 

 mesenteric glands, in the same way as the ascent of sap in plants, 

 during the spring, appears to depend on the constant absorbing action 

 of the roots. 3 It is probable, too, that the vessels themselves are con- 

 tractile: 4 such is the opinion of Messrs. Sheldon, 5 Schneider, Cruik- 

 shank, 6 and J. Miiller. M. Mandl 7 affirms, that it can no longer be 

 doubted; and that the irritability continues even for several hours after 

 death. M. Mojon 8 considers, that when the longitudinal fibres, which 

 he has observed in the lymphatics, contract, they draw one sphincter 

 nearer to another, whilst the oblique fibres diminish the diameter. All 



Muller's Archiv., 1844. 2 Ibid., s. 401, Berlin, 1847. 



3 Breschet, Le Systeme Lymphatique, Paris, 1836. 



4 Miiller's Handbuch, u. s. w., and Baly's translation, i. 284, Lond., 1838. 



5 History of the Absorbent System, p. 28, Lond., 1784. 6 Op. citat., c. 12. 

 7 Manuel d'Anatomie generate, p. 211, Paris, 1843. 



* Journ. de la Societe des Sciences Physiques, etc., Nov., 1 833. 



