96 
Proceedings of Royal Society of Edinburgh. [sess. 
Note on the Digestion of Starch in the Stomach. 
By W. G. Aitchison Robertson, M.D., D.Sc. 
(Read April 6, 1896.) 
Effect of Normal Gastric Secretion on Amylolysis by Ptyalin . 
The following experiments were performed with normal human 
gastric secretion. After thoroughly washing out the stomach of a 
healthy man, several ounces of a dilute solution of Caffyn’s liquor 
carnis were introduced into it. After the lapse of an hour the 
contents of the stomach were drawn off, filtered, and used instead 
of the pure acid solutions in former experiments. The acidity of 
the -gastric fluid was due to inorganic acid and amounted to 0T5 
per cent, hydrochloric acid. 
10 c.c. gastric secretion, \ Acidity 
10 c.c. 1 % starch solution, l = Q-05 % HC1. 
10 c.c. saliva, ) At 38° C. 
This experiment shows that, in the stomach, with an acidity of 
the contents less than that even normally present in the gastric 
secretion, the action of ptyalin is wholly restrained. 
Was the ferment merely inhibited from action by the acid, or 
was it destroyed % 
To determine this, I took equal volumes of this gastric fluid, 
1 per cent, starch solution, and saliva, and having mixed them, 
carefully neutralised the mixture with a solution of caustic potash, 
using very delicate test-papers to show the neutral point. 
10 c.c. healthy gastric fluid, \ Carefully / Starch wholly con- 
10 c.c. 1 % starch solution, > neutralised. < verted within 
10 c.c. saliva, ) At 38° C. ( ten minutes. 
On examining the mixture shortly after neutralisation, the whole 
of the starch was found to have undergone conversion. It reduced 
Fehling’s solution strongly, and contained 0*22 per cent, of re- 
ducing substance. This demonstrates that, with an acidity equal 
ij Starch unchanged 
after two hours. 
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