A NEW TEST OF THE NUTRITIVE VALUE OF FOODS. 143 



gastric juice and the smallest quantity of pancreatic fluid are poured 

 out on milk, consequently the secretory activity requisite for its 

 assimilation is much less than with any other food-stuff. In addition, 

 milk possesses a further important property. Thus, when it is intro- 

 duced unobserved into the stomach of an animal it causes a secretion 

 both in the stomach and also one from the pancreas, consequently 

 it appears to be an independent chemical excitant of the digestive 

 canal, and in this action it is remarkable that we perceive no essential 

 difference in the effect when the milk is brought unnoticed into 

 the stomach from that which occurs when it is given to the animal 

 to lap. Although flesh is a better chemical excitant, it is by no 

 means a matter of indifference how it gets into the stomach. It 

 must, therefore, be accepted that milk excites not only a really 

 effective, but at the same time a very economic, secretion, and also 

 that the appetite is unable to stimulate this secretion into a more active 

 or abundant flow. The secret of the relation of milk to the secretion of 

 the digestive juices can, unfortunately, at present be submitted to no 

 further analysis or investigation. We are at liberty, however, to 

 suppose that the fat on the one hand is of importance for the inhibition 

 of the gastric glands, and the alkalinity on the other for the restraint 

 of the pancreas. Thus the gastric glands and the pancreas, notwithstand- 

 ing the presence of excitants, are maintained by milk at a certain 

 but not too high degree of activity, a matter which is in every way 

 desirable in consideration of the easy digestibility of its constituents. 

 Finally, the third characteristic which is observed to belong to milk, 

 and which is probably only an expression of the first, consists in the 

 following. When one administers to an animal equivalent quantities 

 of nitrogen, in the one case as milk, in the other as bread, and after- 

 wards estimates the hourly output of nitrogen in the urine, it results 

 that the increase during the first seven to ten hours after the milk 

 (compared with the excretion beforehand) amounts only to from 12 per 

 cent, to 15 per cent, of the nitrogen taken in, while after bread, 

 it amounts to 50 per cent. If the hourly rate of absorption and 

 the extent to which milk and bread are respectively used up be 

 taken into consideration, it has to be admitted that these augmentations 

 of urinary nitrogen which appear soon after feeding, must be ex- 

 pressions of the functional activity of the digestive canal itself, and that 

 this activity in the case of bread is three or four times greater than in 

 the case of milk (Experiments of Prof. Ejasanzew) ; consequently, in 

 the case of milk a much larger fraction of its nitrogen is free to 

 be used up by the organism at large (irrespective of the organs of diges- 

 tion) than in that of any other kind of food. In other words, the price 

 which the organism pays for the nitrogen of milk, in the form of work 



