CHAP. III.] COMPOSITION OF ANIMALS AND PLANTS. 23 



m-ic acid and the urates, fat bodies (oleine, margarine, stearine), 

 animal starch or glycogenous matter of the liver, the glycose of the 

 same gland, chitine. They comprehend quaternary azotised pro- 

 ducts, the result of the disassLtnilation of the organic elements, 

 such as ui-ea (C^^H^O^), creatine (C^WM^^O*), creatinine 

 (G^WAz^O'}, cholesterine (C^SH^^O^), and so on. While the 

 principles of the first class pass merely 'into the organism by 

 coming from the exterior world, those of the second form them- 

 selves in the animal organism, but do not sojoiirn there. 



The immediate principles of the third class are numerous 

 neither in animals nor plants, but they play in the first a more 

 important part than in the last. They are the alb umin oidal sub- 

 stances, all likewise colloids, and insatiable in their thirst for 

 water. These bodies are very unstable compounds, much inclined 

 to isomeric modifications. They are formed in the animal 

 economy, never leave it when it is in a healthy state, are renewed 

 therein molecule by molecule through the nutritive movement, 

 and from their quantity and from the dominant part they play, 

 they constitute the very essence of the living organism. Their 

 formula, as we have already stated, is still undecided. There has 

 been a disposition to consider them as all formed of the same 

 radical, proteine, united to atoms of sulphur and phosphorus. 



In boiling the epidermic productions, the cartilages, the organic 

 framework of the bones, the cellular tissue, the tendons, and 

 so on, we obtain quaternary azot^ed substances, chondrine, 

 gelatine, containing .less carbon and more a^ote than the other 

 albuminoidal substances : moreover, containing no sulphur. 



The most important animal a lbuminoida l substances are 

 fibrin^, albumin/, caseina/, the analogues of which we have signal- 

 ised in plants. In the same way that in plants we have found 

 a special quaternary substance, chlorophyll, containing a metal, 

 iron, we find also in the superior animals a matter analogous to 

 albumin/, but coagidating much less easily when it is dissolved in 

 water. This matter is the substance of the globules of the 

 blood, globulin^. Like chlorophyll, it contains iron in its com- 



