HUMAN STRUCTURE AND LIFE-ACTIVITIES 481 



obtained by crushing some fresh pancreas and soaking in glycerine 

 as suggested in 399 for extracting pepsin ; or commercial prepara- 

 tions of pancreas extract may be obtained at drug-stores. Add 

 either the glycerine extract or the commercial pancreatic extract to 

 water in test-tubes and also enough sodium carbonate to make the 

 mixture alkaline (as shown by red litmus paper). Starch or protein 

 may be digested in this solution for one or more hours, with tempera- 

 ture between 35 and 40 C., and then tested for osmosis as suggested 

 in 398. Extract of pancreas does not furnish very active lipase, 

 and hence it is difficult to demonstrate the action on fats. 



403. Summary of Digestion and Absorption of Foods. 

 Grape-sugar dissolved in water may be very slightly absorbed 

 in mouth-cavity and esophagus, some in stomach, but 

 chiefly in intestine. Cane and other sugars are changed 

 before absorption in the intestine. 



Starch some digestion to sugar (maltose) in mouth- 

 cavity and in stomach by saliva', but chiefly digested to 

 maltose in intestine by amylopsin of the pancreatic secre- 

 tion. Resulting sugar may be absorbed as stated for sugar 

 above. 



Proteins digested to absorbable form in stomach by 

 pepsin and in intestine by pancreatic secretion. Absorbed 

 to slight extent from stomach, but chiefly from intestine. 

 Milk proteins are coagulated in stomach by rennin as a special 

 preparation for digestion by action of pepsin, or later by 

 pancreatic secretion. 



Fats. Chiefly digested in the intestine by lipase of pan- 

 creatic secretion, aided by bile and intestinal juice. Slightly 

 digested by lipase in the stomach. The protein part of 

 tissues containing fat (e.g., bacon or suet) is digested away 

 in stomach by pepsin, thus freeing the liquid fat. 



Mineral foods. Those that, like common salt, are soluble 

 in water require no change. Others present in various animal 

 and vegetable foods which we commonly use are easily dis- 

 solved in the acid gastric juice. All the mineral foods are 

 ready for absorption when dissolved in water. 

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