THE FUNCTIONS OF THE DIGESTIVE ORGANS. 503 



The total acidity likewise varies according to the nature of the food. 

 It is greatest with meat and least with bread. It is interesting also to 

 note that the duration of the secretion is also regulated according to the 

 nature of the food; and in fact during the course of secretion, from hour 

 to hour, the composition adjusts itself qualitatively to the conditions. 

 We will give here the result of another of Pawlow's experiments: 1 



AMOUNT AND NATURE OF GASTRIC JUICE WITH DIFFERENT 



NOURISHMENT. 



From these figures it is evident that the maximum secretion is produced 

 by meat during the first or second hour. In the case of bread, the max- 

 imum secretion is reached during the first hour, while with milk it is the 

 second or third hour. With meat the juice secreted during the first hour 

 has the greatest digestive power, in bread it is that of the second and 

 third hours, while with milk the maximum digestive power is obtained 

 much later. 



These values do not merely correspond to a single experiment. They 

 have been obtained again and again. At present we cannot say anything 

 concerning the significance of these variations. We can indeed assume 

 that one food requires more ferment for its hydrolysis than another, in 

 order that its decomposition may take place to an equal extent within a 

 given period. We must admit, however, that we are here confronted 

 with many problems which cannot be solved until we know more concern- 

 ing the nature of the ferments themselves and of the fermentation processes 

 which they cause to take place. We introduce these interesting observa- 

 tions here, only to show how well organized are the functions of the diges- 

 tive glands. In this way it is easier for us to understand, in considering 



1 Loc. cit. p. 44. 



