484 OF FOOD, AND THE DIGESTIVE PROCESS. 



642. The application of the substances forming the Albuminous group, to 

 the support of the Animal body, by affording the materials for the nutrition 

 and re-formation of its tissues, needs little explanation. The proportions of 

 the four ingredients of which they are all composed, are so nearly the same, 

 that no essential difference appears to exist among them ; and it is a matter of 

 little consequence, except as far as the gratification of the palate is concerned, 

 whether we feed upon the flesh of animals (fibrine), upon the white of egg 

 (albumen), the curd of milk (caseine), the grain of wheat (gluten), or the seed 

 of the pea (legumin). All these substances are reduced in the stomach to the 

 form of albumen; which resembles the gum of Plants, in being the raw ma- 

 terial, as it were, out of which the various fabrics of the body are constructed. 

 But the rule holds good, with regard to these also, that by being made to 

 feed constantly on the same substance, boiled white of egg, for instance, or 

 meat deprived of the principle (osmazome) that gives it flavour, an animal 

 may be effectually starved ; its disgust at the food being such, that even if it 

 be swallowed, it is not digested. It is very interesting to remark that, in the 

 only instance in which Nature has provided a single article of food for the 

 support of the animal body, she has mingled articles from the three first of 

 the preceding groups. This is the case in Milk, which contains a conside- 

 rable quantity of an albuminous substance, caseine, which forms its curd ; a 

 good deal of oily matter, the butter ; and no inconsiderable amount of sugar, 

 which is dissolved in the whey. The proportions of these vary in different 

 Mammalia ; and they depend in part upon the nature of the food supplied 

 to the Animal that forms the milk ; but the substances are thus combined in 

 every instance. Although the greater part of the organized tissue of Animals 

 is formed at the expense of the Albumen and Fibrine of their blood, yet 

 many of them also contain a large quantity of Gelatine. It seems certain 

 that this gelatine may be produced out of fibrine and albumen ; since in ani- 

 mals that are supported on these alone, the nutrition of the gelatinous tissues 

 does not seem to be impaired. But it also appears, that gelatine taken in as 

 food may be applied to this purpose ; for ordinary experience shows, that be- 

 nefit is derived from jelly, soup, broth, &c. ; peculiarly by persons who have 

 been suffering under exhausting diseases, such as fevers. But it also ap- 

 pears certain, that it cannot be applied to the nutrition of the Albuminous 

 tissues. Some important experiments have been recently made in Paris on 

 this subject, with a view of determining how far the soup made from crushed 

 bones, which constituted a principal article of diet in the hospitals of Paris, 

 was adequate for the support of the patients. The result of these has been 

 quite confirmatory of previous conclusions, namely, that Gelatine may be 

 advantageously mixed with albumen, fibrine, gluten, &c., and those other in- 

 gredients which exist in meat-soup and bread ; but that, when taken alone, it 

 has little more power of sustaining life than sugar or starch possesses ; and 

 that, even when bread is united with gelatine-soup, it does not give it the re- 

 quisite power of nutrition. 



643. If the non-azotized compounds which exist so largely in the food of 

 Herbivorous animals, be not destined to form part (in any considerable degree 

 at least) of their tissues, the question arises, what becomes of them ? It is 

 not enough to say that they are deposited as Fat; since it is only when a large 

 quantity of them is taken in, that there is any increase in the quantity of fat 

 already in the body. We shall hereafter see, that they are used up in the 

 process of Respiration; being burned-ofT within the body, for the purpose of 

 keeping up its temperature. The process will be hereafter considered more 

 in detail ; and at present we need only stop to remark upon the adaptation 

 between the food provided for animals in different climates, and the amount 

 of heat which it is necessary for them to produce. Thus the bears, and seals, 



