INDIFFERENCE TO MECHANICAL STIMULATION. 87 



furnishing a healthy gastric juice. From this it irrefutably follows, 

 that only one explanation is to be found for the negative result in the 

 first half of our experiment, viz., that the mucous membrane of the 

 stomach, so far as secretory activity goes, is perfectly indifferent to 

 mechanical excitation. And yet this mechanical stimulus is demon- 

 strated as an exciting agency in the physiological lecture-theatre. I 

 venture to think that this lecture experiment from now onwards 

 will quit the field, and give place to the one I have just shown you. 

 This apparently simple experiment of mechanical stimulation can, how- 

 ever, only be successfully performed when certain very obvious rules are 

 followed. These, however, physiologists have not observed, probably on 

 account of a preconceived belief in the effectiveness of the mechan- 

 ical stimulus. These rules are two. First, it is necessary that the 

 stomach should be clean, and that nothing shall gain entry to it from 

 without. Such conditions were not formerly fulfilled. It is true the 

 stomach was emptied by removing the stopper from the fistular cannula, 

 but it was not washed out till an acid reaction was no longer given, and 

 consequently preformed gastric juice was left behind between the folds of 

 the mucous membrane. At the same time, saliva from the cavity of 

 the mouth could gain entry, which quickly became acidified in the in- 

 completely emptied and imperfectly washed-out organ. It is, therefore, 

 not surprising that the glass tube, by setting up contractions of the 

 stomach, was the means of expressing small quantities of acid fluid 

 from the fistula-tube. (The relationship between mechanical stimula- 

 tion and the motor functions of the stomach is not to be confounded with 

 what we are here speaking of.) That matters are as I state, and that 

 the facts correspond to the explanation, is proved by this, namely, that 

 nobody till now has obtained genuinely pure gastric juice of an acidity 

 amounting to 0-5 or O'G per cent. It is only necessary to call to mind that 

 Heidenhain, when determining the acidity of the juice first obtained 

 from the resected stomach, was placed in no little doubt as to whether 

 his results (O-.J to ()(!) were correct, and his assistant at the time 

 (Gscheidlen) was set to verify the correctness of his standard solutions. 

 The acidity of the " purest" juice known at that time was scarcely O3 

 per cent. As a further proof that none of the older observers ever 

 really obtained a secretion from mechanical stimulation pure and simple, 

 we may adduce the fact that none of them made mention of the 

 constant and precise period of five minutes' latency. To overlook 

 this was not possible if a genuine excitation of the glands had been 

 obtained. 



Of no less importance is the second condition when we wish to per- 

 form the experiment of mechanical stimulation in the correct way. It is 

 very necessary that the gastric glands be not already in activity at the 



