736 



PHYSIOLOGY 



exact equivalence between the strengths of the juices obtained from each 

 section. We may therefore regard the secretion obtained from the small 

 stomach as a sample of that produced by the large, and from the changes in 

 this small stomach judge of the effects occurring in the whole organ. By 

 this method it is possible to study the effects of a normal meal in which the 

 food is swallowed, or of a sham meal in which the food is merely masticated 

 in the mouth, or of a meal in which the food is directly introduced into an 

 opening into the large stomach. 



The method which we must adopt for the collection of gastric juice shows 

 that we have to do, in the first place, with a reflex nervous mechanism, 

 since an active secretion is excited by the presence of food in the mouth and 

 by its mastication. Moreover a secretion, which is at least as vigorous as that 

 produced by a sham meal, can be evoked by merely arousing in the dog the 

 idea of a meal. If the animal be hungry, it is sufficient to show it the food to 

 produce a secretion. In the experiment from which the following Table is 

 taken, the dog was continually excited by showing it meat during a period 

 of an hour and a half. At the end of this time the animal, which had an 

 oesophageal fistula, was given a sham meal. It will be observed that the 

 psychical secretion obtained during the first period of the experiment was 

 rather greater than the secretion produced by the introduction of food into 

 the mouth. 



PSYCHICAL SECRETION OF GASTRIC JUICE (PAWLOW) 



SHAM FEEDING 



Time 

 17 minutes 



9 

 8 



Quantity 

 10 c.c. 

 10 

 10 



The afferent channels for this reflex may be therefore either the afferent 

 nerves from the mouth or, when the idea of food is involved, any of the nerves 

 of special sense, such as sight, smell, or hearing, through which these ideas 

 are called forth. The efferent channels can be only one of two nerves, viz. 

 the vagus and the sympathetic, since these are the only two which are 

 distributed to the stomach. That it is the former of these nerves which is 

 involved is shown by the fact, recorded by Pawlow, that psychical secretion, 

 as well as the results of a sham meal, is entirely abolished by division of both 



