AND ABSORPTION 35 



pain or tenderness in the cutaneous area also. The 

 pain of peritonitis is probably quite a different thing. 

 Sensation in the intestine corresponds closely in its 

 physiology with sensation in the stomach. The 

 anal canal, however, can detect thermal and tactile 

 stimuli. 



VARIATIONS IN THE HYDROCHLORIC ACID OF 

 THE STOMACH. 



Thus far we have concerned ourselves particularly 

 with the production of pepsin in the gastric juice, 

 and its physiological variations in quantity. It will 

 repay study to inquire also into the behaviour of 

 the hydrochloric acid. The amount normally present 

 as free HC1 is given differently by different physiolo- 

 gists, some following Topfer and relying on amido- 

 azo-benzol as the indicator, others using the more 

 accurate but somewhat tedious method of Willcox.* 



The contradictory results obtained by various 

 workers are worthy of explanation. The significant 

 figure, the 0-2 per cent of HC1, means (a) HC1 which 

 has already got to work on and combined with 

 protein in the food, together with (b) any free HC1 still 

 unattached. Obviously, a larger or more albuminous 

 test-meal would reduce the free HC1 still further in 

 any stomach, however normal the acidity. In spite 

 of this, some still prefer to estimate the free HC1 and 

 to regard it as the significant figure ; they take the 

 normal to be 0-02 per cent after a test-meal, the 

 remaining 0-18 having combined with the food. 



The total acidity of course includes lactic acid and 



* Lancet, 1905, (i), p. 1566. 



