14:6 COMPARATIVE PHYSIOLOGY. 



fatty acids, i. e., the acid radicles of the fatty acids of the oleic 

 and acetic series replace the exchangeable atoms of H in the 

 triatomic alcohol glycerine, e. g. : 



Glycerine. Palmitic acid. Glycerine tripalmitate or palmitiu. 



{ OH HO.OC.CHai i O.CO.CuH,, 



C»H» I OH + HO.OC.Ci^Hsi = CsHs \ O.OO.C.Hs. + SH^O 

 i OH HO.OO.C,5H3i ( O.OO.Oi^Ha, 



A soap is formed by the action of caustic alkalies on fats, .e.g.: 



Tripalmitin. Fotassium palmitate. 



(C.?a;03) [ 0» + 3 (KOH) = 3 j (g«H.O^)o J ^CsH^j ^^ 



The soap may be decomposed by a strong acid into a fatty 

 acid and a salt, e. g. : 



Ci.H„.C0.K: + HCl = CasHsi.CO^H + KCl. 



PotaBsium palmitate. Palmitic acid. 



The fats are insoluble in water, but soluble in hot alcohol, 

 ether, chloroform, etc. 



The alkaline soaps are soluble in water. 



Most animal fats are mixtures of several kinds in varying 

 proportions ; hence the melting-point for the fat of each species 

 of animal is different. 



PECULIAE FATS. 



Lecithin, Protagon, Cerebrin : 



They consist of C, H, N, O, and the first two of P in addi- 

 tion. 



They occur in the nervous tissues. 



CARBOHYDRATES. 



General formula, C„ (HjO)^. , 



1. The Sugars : Dextrose, or grape-sugar, CeHuOe readily 

 undergoes alcoholic fermentation ; less readily lactic fermen- 

 tation. 



Lactose, milk-sugar, CkHkjOi, ; susceptible of the lactic acid 

 fermentation. 



Inosit, or muscle-sugar, CeHuOo ; capable of the lactic fer- 

 mentation. 



Maltose, CiJEaOn, capable of the alcoholic fermentation. 

 The chief sugar of the digestive process. 



All the above are much less sweet and soluble than ordinary 

 cane-sugar. 



