FATS. 



87 



which is a neutral fluid substance, and secondly, a fatty acid, viz: 

 oleic, rnargaric, or stearic acid, corresponding to the kind of fat 

 which has been used in the experiment. The glycerine remains in 

 a free state, while the fatty acid unites with the alkali employed, 

 forming an oleate, margarate, or stearate. This combination is 

 termed a soap, and the process by which it is formed is called 

 1 sapontjication. This process, however, is not a simple decomposition 

 of the fatty body, since it can only take place in the presence of 

 water ; several equivalents of which unite with the elements of the 

 fatty body, and enter into the composition of the glycerine, &c., so 

 that the fatty acid and the glycerine together weigh more than the 

 original fatty substance which was decomposed. It is not proper, 

 therefore, to regard an oleaginous body as formed by the union of a 

 fatty acid with glycerine. It is formed, on the contrary, in all pro- 

 bability, by the direct combination of its ultimate chemical elements. 

 The different kinds of oil, fat, lard, suet, &c., contain the three 

 oleaginous matters mentioned above, mingled together in different 

 proportions. The more solid fats contain a larger quantity of 

 stearine and margarine ; the less consistent varieties, a larger pro- 

 portion of oleine. Xeither of the oleaginous matters, stearine, 

 margarine, or oleine, ever occur separately; but in every fatty sub- 

 stance they are mingled together, so that the more fluid of them hold 

 in solution the more solid. 



Generally speaking, in the Flg * 7 * 



living body, these mixtures 

 are fluid, or nearly so; for 

 though both stearine and 

 margarine are solid, when 

 pure, at the ordinary tem- 

 perature of the body, they 

 are held in solution, during 

 life, by the oleine with which 

 they are associated. After 

 death, however, as the body 

 cools, the stearine and mar- 

 garine sometimes separate 

 from the mixture in a crys- 

 talline form, since the oleine 

 can no longer hold in solu- 

 tion so large a quantity of them as it had dissolved at a higher 

 temperature. 



STEARISE c ystallized from a Warm Solution in 

 Oleine. 



