PRINCIPLES OF ORGANIC ORIGIN. 59 



ciples, as hereafter explained) by dis-assimilation, they constitute a 

 part of the organized substance of the body only in an accessory 

 manner, and not as original constituents of the tissues. Hence they 

 are rejected from the body (except fat) almost as soon as formed, 

 mostly in the bile and urine. 1 Their accumulation, indeed, is inju- 

 rious, and, as in the case of urea and others, may prove fatal. Even 

 fat, accumulating in the epithelial cells of the kidney or the liver, 

 and in other cases of fatty degeneration, produces death. Yery 

 corpulent persons do not attain to an advanced age. 



These principles (except the fatty, so far as they enter into the 

 formation of adipose tissue) are not alimentary, not assimilable. 

 Only the first and the third classes are so. Hence our food must 

 contain these last, while it does not contain the principles under 

 consideration. The fatty compounds, however, are required in the 

 food for the development of adipose tissue ; and sugar is usually 

 taken in the food, though it may be formed in the body from starch, 

 in case none is thus taken. But no tissue is nourished by it. In 

 any tissue, therefore, except the adipose, in which these principles 

 are found (as lactic acid, creatine, &c., in muscle), they are the result 

 of the waste of the tissue itself. 



Though so numerous (forty-two in all), the principles of the 

 second class constitute a much smaller part of the body than those 

 of the other two classes, since they generally exist in small quanti- 

 ties. Indeed, about two-thirds of them all are contained in the blood, 

 and the urine is next in order in this respect. The bile contains 

 several, also, which the urine does not. 



All these compounds are in the liquid state in the body, except 

 (sometimes) stearine and margarine ; and perhaps the cholesterine 

 of the brain. Some of them may, however, accidentally become 

 solid, and form concretions, as uric acid, cystine, &c. Generally 

 they are liquid by direct solution in water. Stearine and marga- 

 rine, however, when liquid, -are dissolved in oleine. 



But nine simple elements are found in this class sodium, potas- 

 sium, calcium, magnesium, sulphur, carbon, oxygen, hydrogen, and 

 nitrogen. 



Preparatory to their exit from the body, these principles gene- 

 rally pass into the state of carbonates, and then of carbonic acid ; 

 or are rejected in the urine, either unchanged or after isomeric cata- 



1 This class, therefore, includes all the " urinary 'deposits," except the organized 

 (as mucus, pus, and blood), and some of the salts just mentioned. 



