DESTINATION OF NON-AZOTIZED ALIMENTS. 153 
substances are reduced in the stomach to the form of albumen ; 
which is the raw material out of which the various fabrics of 
the body are constructed. But the rule holds good with re- 
gard 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 that gives it flavour,—an animal may 
_ be effectually starved ; its disgust at the food being such, that 
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even if it be swallowed it is not digested. It is very interest- 
ing 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 preceding 
ps. This isthe case in Milk ; which contains a consider- 
able quantity of the albuminous substance, casein, that forms 
its curd ; a good deal of oily matter, the butter; and no in- 
considerable amount of sugar, which is dissolved in the whey. 
The proportions of these vary in different Mammalia, being 
related as it would seem to the habits of the young animal 
thus sustained, while they depend in part upon the nature of 
the food supplied to the animal that forms the milk ; but the 
three substances are thus combined in every instance. 
159. But although the greater part of the organised tis- 
sues of animals have a composition nearly allied to that of 
albumen, many of them also contain a large quantity of 
gelatin (§ 19). It seems certain that this gelatin may be pro- 
duced out of albuminous substances ; since in animals that 
are supported on these alone, the nutrition of the gelatinous 
tissues does nct seem to be impaired. But it appears equally 
certain, that gelatin cannot be applied to the nutrition of the 
albuminous tissues. Many series of experiments have been 
made on this subject, with a view of determining how far 
. gelatin-soup made from crushed bones (such as that which 
_ long constituted a principal article of diet in the hospitals of 
Paris) is adequate for the support of the body in health. 
_ The result of these has been uniformly the same,—namely, 
_ that although gelatin may be advantageously mixed with 
albumen, fibrin, gluten, &c., and those other ingredients which 
exist in meat-soup and bread, yet that, when taken alone, it 
has little (if any) more power of sustaining life, than sugar 
_ or starch possesses. Although it might have been thought 
: likely that gelatin employed as food might be applied within 
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_ the body to the nutrition of its gelatinous tissues, yet there 
