IDENTITY OF ANIMAL AND VEGETABLE PRINCIPLES. 



370 



elements they assimilate. It might be expected from this, that the 

 material constitution of animals should approach, and sometimes even 

 be identical with that of vegetables ; and it is found, in fact, that a 

 considerable number of ternary or quarternary organic compounds, 

 of either kingdom, present the greatest analogy to one another ; their 

 identity, in some cases, is even complete. Some fatty substances 

 of animal origin do not differ in any way from vegetable fats ; the 

 margaric acid which is obtained from hog's lard has the precise 

 characters of the margaric acid which is furnished by olive oil, and 

 the same identity is preserved through the entire series of quarter- 

 nary azotized principles, as a glance at the following table, which 

 contains the results of the analyses performed by Messrs Dumas 

 and Cahours, will show. 



These principles, to which must be added gelatine, the fats and 

 several earthy and alkaline salts, constitute the frame-work of the 

 animal tissues, or the fluids which penetrate them ; it is therefore 

 necessary for us to examine each of them shortly. 



Gelatine is met with in almost all the solid parts, in the bones, 

 tendons, cartilages, skin, cellular tissue, muscular flesh — all contain 

 it. It is readily soluble in boiling water ; cold water only takes up 

 a small quantity of it. Two or three parts of gelatine dissolved in 

 100 parts of hot water, suffice to turn the fluid into a tremulous jelly 

 when it has become cold. Tannin, or infusion of gall-nuts, precipi- 

 tates gelatine completely from its solution, the precipitate being very 

 bulky and perfectly insoluble in water ; and it is this chemical com- 

 bina bn or principle which lies at the bottom of the art of tanning. 



Gelatine is extensively used in the arts, under the familiar name 



of glue. Isinglass consists of gelatine nearly pure, and, according 



to Mulder, contains : 



Carbon. 50.8 



Hydrogen 6.6 



Azote 18.3 



Oxygen 24J 



100.0 



Fihrine occurs in a state of solution in the blood, and forms the 

 principal ingredient in muscular flesh. It is readily obtained by 

 whipping a quantity of blood just taken from the veins of a living 

 animal ; the white stringy masses that adhere to the rod are fibrine, 

 which, by gentle kneading under water, become colorless. Fibrine, 



