460 ABSORPTION. 



are taken up by the lacteals, and may be absorbed in small 

 quantity by the blood-vessels. Though it is now pretty well 

 understood how endosmotic liquids pass through the walls 

 of the blood-vessels and absorbents, the mechanism of the 

 penetration of fatty particles, which is no less constant, is 

 still somewhat obscure. We cannot at the present day in- 

 voke the aid of orifices in the vessels in explanation of this phe- 

 nomenon ; for the opinion of the best anatomists is decidedly 

 against the existence of these orifices in the lacteal capillaries, 

 though some still adhere to the view that they really exist, 

 and it is certain that there are no such openings in the capil- 

 lary blood-vessels. 1 



There can be no question with regard to the actual pene- 

 tration of the minute particles of the chyle into thelacteals, 

 and even into the blood-vessels. In birds, indeed, all the fat 

 which is absorbed is taken up by the blood-vessels, the lym- 

 phatics .of the intestine never containing a milky fluid. 2 

 Assuming, then, that the walls of these vessels have no 

 orifices through which the fatty particles can pass, it is 



1 It is chiefly with reference to the penetration of fatty particles that the 

 question of the existence or non-existence of orifices in the smallest lacteals is 

 interesting. Cruikshank, who wrote an elaborate memoir on the anatomy of 

 the absorbent system, in the latter part of the last century, not only .admits 

 the existence of these openings, but actually estimates their number in each 

 villus. He examined the villi in the intestines of a woman who had died sud- 

 denly, and in whom the lacteal system was filled with coagulated chyle. He and 

 Dr. William Hunter examined the villi with the microscope, estimating about 

 fifteen or twenty openings on each villus, in the jejunum. (CRUIKSHANK, The 

 Anatomy of the Absorbing Vessels of the Human Body, second edition, London, 

 1790, p. 59). Kb'lliker (Manual of Human Microscopic Anatomy, London, 1860, 

 p. 329) describes striae in the cell-wall, which he remarks may possibly be at- 

 tributed to extremely fine canals. Beaunis (Journal de la Physiologic, Paris, 

 1863, tome vi., p. 339) quotes and confirms the observations of Kecklinghausen 

 (VIRCHOW'S Archiv, Berlin, 1862, Bd. xxvi., S. 188), who professes to have 

 demonstrated openings in the lacteals by filling them with a solution of nitrate of 

 silver, when the openings presented the appearance of black points. In none of 

 these observations, is the evidence sufficiently conclusive to warrant the assump- 

 tion of the existence of openings in any part of the absorbent system. 

 2 BERNARD, Lecons de Physiologie Experimental, Paris, 1856, p. 317. 



