DIGESTION. 83 



and wash the precipitate two or three times. 

 Add some of this coagulated casein to 10 c.c. 

 of pancreatic juice and place in the warm 

 water-bath. Normally, what curdles the milk? 

 What is the effect of the pancreatic juice on 

 the curd? 



2. Mix 20 c.c. of the milk and 10 c.c. of pan- 



creatic juice. Place in the warm bath and 

 watch for results. After an hour what has 

 occurred? The precipitate is casein. Is it 

 in fine particles or in solid clots? 



3. This experiment is to be performed after the 



milk has been digested in experiment 2 for 

 an hour. Place in one test-tube 10 c.c. of 

 fresh milk and in another 10 c.c. of the milk 

 of experiment 2. Add to each the same 

 amount, about 15 c.c. of acetic acid or vinegar. 

 In which is the clot more firm ? Milk is often 

 treated with pancreatin or " peptonized " for 

 children and invalids. Why ? 



D. Absorption of the Soluble Products of Digestion. 



After the food has been acted upon by the various 

 digestive fluids of the alimentary canal, it is ready to 

 supply nourishment to the body. The products of diges- 

 tion, then, must in some way pass through the walls of 

 the alimentary canal and pass into the blood, in order to 

 reach the various organs of the body. Just how these 

 substances are able to pass through the walls of the intes- 

 tine has long been a question among physiologists. It is 



