DIGESTION IN THE STOMACH 



781 



the animal, the juice always has the same characters, the same 

 digestive power, and the same percentage of hydrochloric acid. 

 He finds, however, that in the case of the second, or what we may call 

 ' chemical ' secretion, i.e. that produced by local changes in the 

 stomach, there is considerable variation in the nature of the juice. 

 In the following Table are shown the relative effects of meat and 

 of milk, when introduced into the large stomach, in determining 

 a flow of juice from the small stomach of an animal with a 

 Pawlow fistula. Whereas the secretion of juice is greatest in amount 

 with the meat, the digestive power of the juice is greatest with the 



bread, and Pawlow regards these differences in the juice as deter- 

 mined by the variations in the stimulus applied to the gastric mucous 

 membrane. It is doubtful, however, whether these results justify us 

 in ascribing a number of specific sensibilities to the gastric mucous 

 membrane. We have seen that the psychical juice depends merely 

 on appetite, and therefore will be greater in amount the more welcome 

 the food is to the animal. On the other hand, the juice secreted in 

 the second phase must vary according to the quantity of gastric 

 hormone produced in the pyloric mucous membrane, and there- 

 fore with the nature and amount of the substances produced in the 

 preliminary digestion of the gastric contents by means of the psychic 

 juice. The amount of juice may vary also with the salts contained 

 in the food, according to their alkaline or acid character, and the 

 percentage of pepsin in the juice may vary with the intensity of 

 stimulus as well as with the quantity of fluid available for the forma- 

 tion of the gastric juice. These factors will co-operate in determining 

 the characters of the whole juice secreted after any given meal, and 

 it seems possible to explain the variations, observed on such different 

 diets as meat and bread, without having recourse to the difficult 

 assumption of a specific sensibility of the gastric mucous membrane 

 to such inert substances as dextrin or egg albumin. 



