XV.] SALIVARY GLANDS AND PANCREAS. SALIVA. 165 



When no starch is left in A, remove G from the 

 ice and place it in the warm chamber and test 

 at intervals as before, the starch soon disappears. 

 Hence a temperature of 0C. arrests the action of 

 saliva but does not destroy it. 



11. Neutralize a small quantity of saliva; to 5 c.c. 

 of this add 5 c.c. of HC1 *2 l p.c., the mixture 

 thus contains 1 p.c. HCL Place at 37 C. 2 for 

 ten minutes, add 3*5 c.c. Na 2 C0 3 *4 p.c. and 

 complete the neutralization with a more dilute 

 solution. Add a few c.c. of starch and place at 

 37 C. In half-an-hour test for starch and sugar; 

 starch will be found but no sugar, hence the 

 acid has destroyed the ptyalin. 



12. Place in one dialyser 3 (A) 15 c.c. of starch and 

 in another (B) 10 c.c. of starch with a little 

 saliva. 



Test from time to time the external water in 

 each. That from (A) will give no trace of 

 starch or sugar. That from (B) will contain 

 sugar, but no starch. Sugar dialyses, but starch 

 does not. 



1 Pure strong commercial hydrochloric acid contains about 33 p.c. 

 HC1. 



3 In these and in similar experiments (Less, xvi.) 37 C. is taken 

 since that is very nearly the normal body temperature of man, but a 

 rather higher or a rather lower temperature will serve equally well. 



* A very convenient dialyser may be made from a short length of 

 parchment paper tubing (Papier-Darme) sold by Carl Brandegger, 

 Ellwangen, Wurttemberg (cp. also Gamgee, Physiological Chemistry, 

 Vol. i. p. 6). 



