456 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



leucocytes, which in the assimilation of albuminoids fill a role analogous 

 to that of the red blood-corpuscles in respiration. He assumes that the 

 reason why peptone cannot be recognized in the blood is because it has 

 combined with these lymphatic cells, and is, through their mediation, 

 transported to different parts of the body ; and he regards the rapid pro- 

 liferation of the cells of the adenoid tissue of the intestinal mucous mem- 

 brane and of the Peyer's patches as a morphological expression of the 

 chemical processes of assimilation occurring in these tissues. 



Thus, it seems that the process of absorption is as much a vital one 

 as that of secretion, and that the epithelial or lymphatic cell not only 

 aids the taking of fat into the blood, but also that of peptone (changing it 

 to albumen), and of sugar and salts. 



2. Absorption by the Lymphatics. — Absorption by the lymphatics is 

 accomplished through the instrumentality of the villi of the small intes- 

 tine. Each villus contains in its axis the 

 commencement of a chyle-vessel, which is 

 surrounded by a fine capillary net-work (Fig. 

 167). 'The chief purpose of this villous for- 

 mation is evidently to obtain an increase of 

 surface for absorption with economy of 

 space ; but each villus has, further, some 

 special mechanism which aids the absorption 

 of the intestinal contents, as is proved by 

 the entrance into the chyle-vessels of 

 globules of oil after having undergone emul- 

 sification by the bile and pancreatic juice. 



The fat-globules first enter the proto- 

 plasmic caps of the epithelial cells, from 

 these pass into the tissue of the villus, and 

 thence into the central chyle-duct (Pig. 168). 

 After an abundant fatty diet, this absorption of fat may be so active as 

 to completely fill the net-work of lymphatics of the mesentery with 

 milk-white, emulsified oil, and even sometimes give the blood-serum a 

 milky-white color (Fig. 169). It further appears that the fat which is 

 absorbed in a state of emulsion by these chyle-vessels is greatly in 

 excess of the saponified fatty acids which may be absorbed by the 

 veins; for, after a fat diet, nearly two-thirds of the amount of fat given 

 as food may be recovered from the thoracic duct. 



As regards the mechanism of fat absorption, the most probable view 

 attributes the entrance of the oil-globules into the epithelial cells of the 

 villus to a true, protoplasmic, selective power exerted by the contents 

 of these cells, and entirely analogous to the mechanism of feeding pos- 

 sessed by the amoeba and other infusoria. 



Fig. 168. — Diagram op the 

 Relation of the Epi- 

 thelium to the Lacteal 

 Radical in a Villus, 

 after funke. 



The protoplasmic epithelial cells are 

 supposed to be connected to the absorbent 

 vessel by adenoid tissue. 



