98 
Proceedings of Royal Society of Edinburgh. [sess. 
starch had been changed into the higher or achroodextrins), and 
contained 0T38 per cent, reducing substance. 
These experiments show that, with the degree of acidity found 
in the above secretions, the ferment ptyalin is not killed, but its 
converting action is prevented. The diastatic action of the saliva 
seems also to become weaker the longer it is exposed to the in- 
fluence of the acid, as is shown in the second case, where the 
ptyalin was exposed to the action of the acid for twenty-four 
hours. In this case the converting action was feeble and very 
slow compared with its action when exposed to the influence of 
the acid for one hour only. 
I am inclined to believe, therefore, that, as the acidity of the 
gastric contents increases during digestion, so is the power of the 
ferment ptyalin diminished, till, at the end of digestion, it must be 
almost, if not entirely, destroyed and rendered incapable of resum- 
ing its function in the small intestine. 
Digestion of Starch in the Stomach. 
To determine whether the gastric secretion per se had any effect 
on starch, I performed the following experiments : — 
I. Healthy Gastric Secretion. — I placed 30 c.c. of a 1 per cent, 
solution of starch in a vessel with 10 c.c. of gastric secretion from 
a healthy individual (the acidity of the latter was equal to 0-211 
per cent, hydrochloric acid), and kept all at a temperature of 38° C. 
There was absolutely no change in the starch even after the lapse 
of two hours. 
30 c.c. 1 % starch solution, 
10 c.c. healthy gastric secretion 
= 0-211 % HC1, 
II. Chronic Gastric Catarrh. — With the secretion from an indi- 
vidual suffering from chronic gastric catarrh I performed a similar 
experiment and with a similar result. 
f 
At 38° C. 
No conversion within 
two hours. 
30 c.c. 1 % starch solution, 
10 c.c. unhealthy gastric secre- 
tion =0 -30 % HC1, 
At 38° C. 
No conversion after 
lapse of two hours. 
