172 



ABSORPTION. 



Fig. 44. 



INTESTINAL EPITHELIUM; from the Dog, while 

 fasting. 



endosmometer, together with a watery alkaline solution of similar 

 strength, it was found that the oily particles penetrated through the 



animal membrane without 

 much difficulty, and mingled 

 with the fluid on the opposite 

 side. Although, therefore, 

 we cannot explain the exact 

 mechanism of absorption in 

 the case of fat, still we know 

 that it is not in opposition to 

 the ordinary phenomena of 

 endosmosis ; for endosmosis 

 will take place with a fatty 

 emulsion, provided the fluids 

 used in the experiment be 

 slightly alkaline in reaction. 

 It is, accordingly, by a pro- 

 cess of endosmosis, or imbi- 

 bition, that the villi take up 



the digested fatty substances. There are no open orifices or canals, 

 into which the oil penetrates ; but it passes directly into and through 



the substance of the villi. 

 The epithelial cells covering 

 the external surface of the 

 villus are the first active 

 agents in this absorption. In 

 the intervals of digestion (Fig. 

 44) these cells are but slightly 

 granular and nearly trans- 

 parent in appearance. But if 

 examined during the diges- 

 tion and absorption of fat 

 (Fig. 45), their substance is 

 seen to be crowded with oily 

 particles, which they have 

 taken up from the intestinal 



from the Dog, during , , ,. rpn 



cavity by absorption. Ihe 

 oily matter then passes on- 

 ward, penetrating deeper and deeper into the substance of the villus, 

 until it is at last received by the capillary vessels and lacteals in its 

 centre. 



INTESTINAL EPITHELIUM 

 the digestion of fat. 



