134 GENERAL ANATOMY. 



of a sweet and disagreeable taste; its yellowish colour is owing 

 to a colouring principle that is soluble in water and carried off 

 in washing. It is not so heavy as water, its fusibility varies 

 according to its composition : it is, in general, fluid at the tem- 

 perature of the body and under it, sometimes even greatly so, 

 as at 15R. for instance; it is insoluble in water, and-but little so 

 in cold alcohol: it is not acid ; that which Crell admitted it to 

 contain, is the result of distillation, an operation, in which fat 

 gives out carbonic, acetic, and sebaic acids, with several other 

 products of the reaction of its elements. It is converted into 

 a sweet principle, and the margaritic and oleic acids, by the 

 action of strong alkaline bases. Exposed to the air and light 

 it becomes rancid, producing a volatile acid of a strong smell. 

 The elementary composition of several of the fats, has been 

 determined by M. M. Berrarde, and Th. de Saussure; it is a 

 combination of carbone, hydrogen and oxygen, varying in 

 proportion, according to the kind of animal: that of human fat 

 has not been determined. 



Previous to the labours of M. Chevreul,* fat was considered 

 as a simple principle. He has demonstrated that it is essen- 

 tially formed of two organic materials j stearine, fusible at 

 about 50 R. and elaine, fluid at zero; it is from the proportion 

 of these, that results the degrees of fusibility of each kind of 

 fat. These two direct materials are separated by treating the 

 fat with boiling alcohol; by cooling, the greater part of the 

 stearine is precipitated along with a little elaine, the latter re- 

 mains in solution, in the alcohol, with a small part of stearine. 

 We can also separate them by congelation, which first fixes 

 the stearine with a little elaine. They may also be isolated by 

 the absorption of unsized paper, which takes up the elaine and 

 leaves the stearine on the surface. 



163. The fat of the adipose tissue, is not the only fatty 

 matter found in animal organization, and in that of man in 

 particular. A crystallizable fatty substance is found in the 

 blood. Malpighi, Haller, and others, thought that free fat cir- 

 culated with the blood; this is a mistake, at least, I have never 



* Annuks de, Chimie. torn. xciv. Ann. de. Chim, et de Phys. torn. ii. et vii. 



