ABSORPTION BY LYMPHATICS. 367 



which this subject is at present involved is due rather 

 to imperfect knowledge of the laws which regulate absorp- 

 tion as it occurs in the living body, than to ignorance of 

 the exact microscopic structure of the tissues concerned ; 

 although, even in the latter respect, there is much dif- 

 ference of opinion, and therefore error. There seems to 

 be no doubt that absorption of fatty matters during 

 digestion, from the contents of the intestines, is effected 

 by the epithelial cells which line the intestinal tract, and 

 mainly by those which clothe the surface of the villi, 

 (fig. 80). From these epithelial cells, again, the fatty 

 particles are passed on into the interior of the lacteal 

 vessels (figs. 80 and 81), but how they pass, and what laws 

 govern their so doing, we know not at all. Heidenhain 

 believes that the deeper ends of the epithelial cells are 

 continuous by fine processes with prolongations from 

 connective-tissue corpuscles in the interior of the villus; 

 while he supposes other prolongations from the same cor- 

 puscles to be directly continuous with the fine terminations 

 or rather beginnings of the lacteal vessels. This view 

 deserves consideration if only on account of its ingenuity, 

 but requires confirmation. 



The opinion before referred to, that the epithelial cells 

 exercise a certain selective power over the materials which 

 they absorb, is supported by various circumstances, which 

 will be considered under the head of absorption by the 

 blood-vessels. 



Absorption by the Lymphatic Vessels. 

 The real source of the lymph, and the mode in which its 

 absorption is effected by the lymphatic vessels, are still 

 among the enigmas of physiology. It may, however, be 

 held with tolerable certainty, that the lymph, like the 

 chyle, is. chiefiy of a nutritive nature, capable of a higher 

 organization, and of contributing to the nutrition of the 

 body. Whether it is derived exclusively from the liquor 



