INTESTINE. 187 



that of absorption, which can best be observed in the digestion 

 of fat. By treatment with osmic acid preparations can be made 

 which show all stages of this process. In what form the fat 

 enters the cells is unknown, but it is probable that it is not as 

 an emulsion, but as fatty acids formed by combination with the 

 bile salts. In the epithelial cells the fatty acids are converted 

 again into neutral fats. It then appears in the intercellular 



FIG. 343. 



border 



. ~ Epithelium 



Tunica -propriii^jA ' Cf^ilbu 



** **% 



cell 



!v;*|* 



Blood capillaries.. -._ ^^^i N #3 * * * SB** t * * 



.. 7 / .. : 'j 1 



Loiigitudiual section through the end of a villus from the small intestine of a cat. X 450. 



spaces in the form of fine globules which pass through the 

 basal membrane. From here it reaches the lymph spaces of 

 the parenchyma of the villus, and finally enters the central 

 chyle vessel or lacteal. This power of fat absorption is not 

 possessed by the epithelium of the large intestine. 



The second important function of the intestinal epithelium, 

 namely, that of secretion, is carried out in great part by the 



