78 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



secretion ceases, and in the dog 0"3 gramme of ' peptone ' per kilo- 

 gramme of body weight is sufficient to kill the animal. 



The epithelial cells of the alimentary canal thus protect us from 



Tin. 26.— Section of the villus of a rat killed during fat-absorption (E. A. Schafer) : 

 ep, epithelium ; str, striated border ; c, lymph cells ; c'. lympli cells in the epithelium ; 

 I, central lacteal containing disintegrating lymph cells. 



those poisonous effects by converting the harmful peptone into the 



useful albumin and globulin. 



Absorption of Fats. — The fats undergo in the intestine two 



changes : one a physical change (emulsification), the other a chemi- 

 cal change (saponifica- 

 tion). The lymphatic 

 vessels are the great 

 channels for fat absorp- 

 tion, and their name, 

 lacteals, is derived from 

 the milk-like appearance 

 of their contents (chyle) 

 during the absorption of 

 fat. 



The way in which the 

 minute fat globules pass 



from the intestine into the lacteals has been the subject of much 



Fig. 27.— Mucous membrane of frog's intestine during fat 

 absorption (E. A. Schafer) : ep, epithelium ; str, striated 

 border ; c, lymph cells ; I, lacteal. 



