THE FUNCTIONS OF THE DIGESTIVE ORGANS. 501 



was taken directly from the fistula than when the latter was closed for a 

 time. The reason for this can be explained. The gastric juice flows over 

 the walls of the stomach, which are covered with alkaline mucus, before 

 it reaches the fistula. When there is a considerable amount of the juice 

 being secreted, it is obvious that proportionately less hydrochloric acid 

 will be neutralized than when only a small amount of juice passes over 

 these walls; and similarly when the fistula is closed, the acid is more com- 

 pletely neutralized by the alkaline mucus than when it passes off freely. 

 As Pawlow has stated, in a normal stomach as much as 25 per cent of the 

 original acidity may be neutralized by the mucus. There are, to some 

 extent, very complicated processes concerned in this neutralization the 

 significance of which cannot be entirely disregarded. It is indeed possible 

 that certain relations exist between the hydrochloric acid content of the 

 stomach juices and the formation of the mucus by the membrane of the 

 stomach, and that here again there is an adjustment corresponding to 

 the nature of the different foodstuffs. Naturally the deviations in the 

 acidity of the stomach juices vary much more greatly after the food has 

 reached the stomach. At all events, any values obtained in this case 

 should be very cautiously applied to the composition of the juice itself. 

 The clinical practitioner must always have in mind all sorts of different 

 relations, and should determine the combined hydrochloric acid as well 

 as that which is still free. The careful physician should never be satisfied 

 with a single observation, but should base his judgment upon examina- 

 tions carried out under the most varied conditions. 



Pawlow calls attention to the adaptability of the whole work of the 

 stomach, and especially of its glands. This is shown in a number of little 

 ways, and we are able to trace the functions of the stomach very well 

 because we know the condition of the food as it enters. Such relations 

 are much more difficult to establish in the study of the pancreas, and in 

 some cases it is impossible, because its juices come in contact, under 

 normal conditions, with an inextricable mixture consisting partly of 

 decomposition products, and partly of unchanged food. Investigations 

 have shown that a mixed diet, as well as the feeding of single articles, such 

 as milk, bread, meat, etc., leads to a perfectly definite formation 

 of the gastric juice. This is true not only of the composition of the fluid, 

 but of the amount secreted and the duration of the secretion. First of 

 all it is to be noted that the amount of gastric juice secreted is practically 

 proportional to the amount of food. Thus 100 grams of raw meat caused 

 the secretion of 26.0 cubic centimeters of juice; 200 grams = 40.0 cubic 

 centimeters; 400 grams = 106.0 cubic centimeters. For a mixed diet, 

 composed of milk, bread and meat, the following values were obtained : 

 100 cubic centimeters of milk, 50 grams meat, and 50 grams of bread, 

 correspond to 42.0 cubic centimeters of gastric juice, while double the 



