ON ORGANIC CHEMISTRY. 49 



Every portion of these substances which escapes this process of oxidation, is 

 sent back into the circulation in the form of bile, which by degrees com- 

 pletely disappears. 



This view of Liebig's, of the use of bile, is highly iugenious and important. 

 In the young of carnivorous animals, the circulation and the respiration are 

 more rapid ; but an infinitely wise Providence has furnished in the butter of 

 the milk of the mother a highly carbonaceous substance, by which the loss of 

 the organized tissues by the action of the oxygen of the air is prevented. In 

 the young of carnivorous birds milk is not required, because the absence of 

 all motion is an obvious cause of a diminished waste in the organs. 



It is obvious also, that in the system of the graminivora, whose food con- 

 tains relatively so small a proportion of the constituents of the blood, the 

 process of metamorphosis in existing tissues, and consequently their restora- 

 tion or reproduction, must go on far less rapidly than in the carnivora. Were 

 this not the case, a vegetation a thousand times more luxuriant would not 

 suffice for their sustenance. Sugar, gum and starch, which form so large 

 a proportion of their food, would then be no longer necessary to support life 

 in these animals, because in that case the products of waste, or metamor- 

 phosis of the organized tissues, would contain enough of carbon to support 

 the respiratory process. 



Man, when confined to animal food, requires sources of nutriment more 

 widely extended than the lion and tiger, because when he has an opportunity 

 he kills without eating. This is the reason that a nation of savage hunters 

 cannot multiply themselves beyond a certain extent; but when civiliza- 

 tion reaches them, and they become herbivorous as well as carnivorous, 

 the population rapidly increases. When exercise is denied to gramini- 

 vorous and omnivorous animals, this is tantamount to a deficient supply of 

 oxygen. The carbon of the food not meeting with sufficient oxygen to con- 

 sume it, it passes into other compounds containing a large excess of carbon 

 and deficiency of oxygen, or, in other words, fat is produced. It is thus that 

 the sedentary ladies of oriental countries acquire so much embonpoint, and 

 stall-fed animals so much fat. That fat does arise in some such way as Liebig 

 describes is obvious ; for the herbs and roots consumed by the cow contain 

 no butter ; in the hay or other fodder of oxen no beef-suet exists ; no hog's- 

 lard can be found in the potato refuse given to swine ; and the food of geese 

 or fowls contain no goose-fat or capon-fat. The fat must be formed in the 

 organism, and for this purpose oxygen must be separated from the carbona- 

 ceous constituents of food. Liebig is led to the startling conclusion, that fat 

 is altogether an abnormal and unnatural production, arising from the adapta- 

 tion of nature to circumstances, and not of circumstances to nature, altogether 

 resulting from a disproportion of carbon in the food to that of the oxygen 

 respired by the lungs or absorbed by the skin. Wild animals in a state of 

 nature do not contain fat. The Bedouin or the Arab of the desert, who 

 shows with pride to the traveller his lean, muscular, sinewy limbs, is altoge- 

 ther free from fat. And the Professor points out the diseases arising from 

 this cause, and furnishes some valuable hints to therapeutics. 



From all that has preceded, we may sum up the nutritious elements of food 

 as follows. The ingredients adapted for the formation of the blood, and 

 which the Professor calls the plastic elements of nutrition, are as follows : — 

 Vegetable fibrine. 

 Vegetable albumen. 

 Vegetable casein. 

 Animal flesh. 

 Animal blood. 



1842. e 



