NATURE AND DESTINATION OF THE FOOD OF ANIMALS. 321 



and, like them, may be deposited in the form of Adipose matter. There is no 

 other tissue in the body into which they can enter without considerable 

 change; for all others are azotized; and it is a most important question, 

 whether the non-azotized compounds can, under any circumstances, be con- 

 verted within the body into compounds of the albuminous or gelatinous groups. 

 This question can scarcely be regarded as having yet received a definitive 

 answer; but the prevalent opinion amongst Chemists is opposed to the possi- 

 bility of such transformation. To this question we shall hereafter revert: and 

 at present we may be satisfied with remarking, that many alimentary sub- 

 stances constituting the staple food of large bodies of men, such as Rice and 

 Potatoes, which were formerly supposed to be entirely made up of starchy 

 matters, are now known to contain azotized compounds of the Albuminous 

 group, to an amount easily recognizable. Whether their quantity be suffi- 

 cient for the requisite nutrition of the Albuminous tissues of the Human body, 

 is a question to be determined by further investigation. At present, the whole 

 subject of inquiry is so new, that it would be premature to offer a decided 

 opinion. (See 567). 



431. 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 ( 457); 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 (fibrin), upon the white 

 of egg (albumen), the curd of milk (casein), 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 

 material, 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 all the three pre- 

 ceding groups. This is the case in Milk, which contains a considerable quan- 

 tity of an albuminous substance, casein, \vhich forms its curd; a good deal of 

 oily matter, the butter ; and no inconsiderable amount of sugar, which is dis- 

 solved 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 Fibrin of their blood, yet many of them also 

 contain a large quantity of Gelatin. It seems certain that this gelatin may be 

 produced out. of fibrin and albumen; since in animals that are supported on 

 these alone, the nutrition of the gelatinous tissues does not seem to be impaired. 

 But it also appears, that gelatin taken in as food may be applied to this pur- 

 pose ; for ordinary experience shows that benefit is derived from jelly, soup, 

 broth, &c. ; peculiarly by persons who have been suffering under exhausting 

 diseases, such as fevers. But it also appears 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, 



