OF FOOD. 109 



to deteriorate, and became very much disturbed before the termi- 

 nation of the experiment. The prominent symptoms were debility, 

 headache, pyrosis, and palpitation of the heart. After the starchy 

 diet was abandoned, it required some days to restore the health to 

 its usual condition. 



The proximate principles of the third class, or the organic sub- 

 stances proper, enter so largely into the constitution of the animal 

 tissues and fluids, that their importance, as elements of the food, is 

 easily understood. No food can be long nutritious, unless a certain 

 proportion of these substances be present in it. Since they are so 

 abundant as ingredients of the body, their loss or absence from the 

 food is felt more speedily and promptly than that of any other sub- 

 stance except water. They have, therefore, sometimes received the 

 name of "nutritious substances," in contradistinction to those of 

 the second class, which contain no nitrogen, and which have been 

 found by the experiments of Magendie and others to be insufficient 

 for the support of life. The organic substances, however, when 

 taken alone, are no more capable of supporting life indefinitely than 

 the others. It was found in the experiments of the French " Gela- 

 tine Commission" 1 that animals fed on pure fibrin and albumen, as 

 well as those fed on gelatine, become, after a short time, much en- 

 feebled, refuse the food which is offered to them, or take it with 

 reluctance, and finally die of inanition. This result has been 

 explained by supposing that these substances, when taken alone, 

 excite after a time such disgust in the animal that they are either 

 no longer taken, or if taken are not digested. But this disgust 

 itself is simply an indication that the substances used are insufficient 

 and finally useless as articles of food, and that the system demands 

 instinctively other materials for its nourishment. 



The instinctive desire of animals for certain substances is the 

 surest indication that they are in reality required for the nutritive 

 process ; and on the other hand, the indifference or repugnance 

 manifested for injurious or useless substances, is an equal evidence 

 of their unfitness as articles of food. This repugnance is well de- 

 scribed by Magendie, in the report of the commission above alluded 

 to, while detailing the result of his investigations on the nutritive 

 qualities of gelatine. "The result," he says, "of these first trials 

 was that pure gelatine was not to the taste of the dogs experimented 

 on. Some of them suffered the pangs of hunger with the gelatine 



1 Cotnptes Rendus, 1841, vol. xiii. p. 2 7. 



