76 



perfectly, assuming the whitefish of our experiments to be analogous to the 

 English whiting." 



It thus appears that Messrs. Chittenden and Cummins found 

 considerable divergence in the digestibility of the flesh of fish 

 of different kinds. These they attribute in part to the varying 

 proportions of fat, the fatter fish being the less digestible, and 

 in part to other characteristics of the flesh. My own impression 

 is, that experiments on the actual digestion in the alimentary 

 canal, in which other juices as well as the gastric come in play 

 and other conditions are different, would show less difference in 

 the digestibility of fish of different sorts than these investi- 

 gators found in their experiments in artificial digestion with 

 gastric juice alone, and also that there would be less variation 

 in the actual quantities and nutritive material digested than the 

 statements made by the authors quoted by Messrs. Chitten- 

 den and Cummins would imply. For we must not forget 

 the distinction between the quantity digested and the ease of 

 digestion. But, of course, this is a matter to be determined by 

 actual experiment and observation. 



The ways in which the experiments for testing the digesti- 

 bility of foods by men and animals are made, are very ingenious 

 and interesting. Physiologists use the salivary glands, or 

 stomach or intestine of a living animal, much as chemists do 

 their bottles and retorts and test-tubes. It is easy to get into 

 the way of regarding an animal as simply an organism manifest- 

 ing certain reactions under given conditions, and in not a few 

 European laboratories a janitor is readily induced by the price 

 of a few months' supply of beer, or a student by his scientific 

 ardor to take this same altruistic view of his own physical 

 organism. In the German laboratories, particularly, one finds 

 not only the needed apparatus, but what is no less important, 

 trained assistants and servants, so that one is relieved of much 

 of the time-consuming and disagreeable detail of experimenting, 

 which is so much of an obstacle with us. 



THE QUANTITIES OF DIGESTIBLE SUBSTANCES IN FOOD. 



The first question we have now to ask may be put in this 

 way. What proportion of each of the nutrients in different 



