XXXV. Salivary digestion. 



/. Materials. Bread; fibrin; pig-fat; olive oil; starch 



paste; cane sugar. 

 2. Preparation. 



Remove the parotid and submaxillary glands of several 

 rabbits or rats, hash them; rinse quickly with water to 

 remove blood; cover with water. After a few hours 

 (12-24) filter or strain off the opalescent aqueous ex- 

 tract. It should contain an aqueous solution of ptya- 

 lin. Label: Salivary Extract. 



(2) Chew a piece of rubber or paraffin. The flow of 

 saliva is stimulated; catch the secretion in a beaker; 

 dilute and filter. Label: Salivary Secretion. 



(3) Fibrin for use in experiments on digestion may be 

 procured in any quantity at a slaughter house. Rid it 

 of all red coloring matter and of accidental contamina- 

 tion by repeatedly soaking and washing in water. The 

 white, elastic shreds of fibrin may be kept indefinitely 

 in pure glycerin. For use one needs only to wash 

 out the glycerin thoroughly. 



j. Experiments and Observations. 



(1) Subject saliva (a) and (^) to the Fehling test. 

 It will be found that neither the extract nor the secre- 

 tion will reduce the CuSO 4 . 



(2) Subject starch paste to the same test. The result 

 is negative. 



(3) Mix equal volumes of starch paste and salivary 

 extract in a beaker. Place the mixture in the incu- 

 bator, which is kept at a temperature of 35 to 40 C. 



157 



