140 ANIMAL PHYSIOLOGY. 
Most animal fats are mixtures of several kinds in varying. 
proportion ; hence the melting-point for the fat of each species 
of animal is different. 
PECULIAR 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,, (H,0),. 
1. THE Suaars: Dextrose, or grape-sugar, CsH»O, + H.O 
readily undergoes alcoholic fermentation; less readily lactic 
fermentation. 
Lactose, milk-sugar, C::£H»On + H,O ; susceptible of the lactic 
acid fermentation. 
Inosit, or muscle-sugar, C.H,,0, + 2H,0; capable of the lac- 
tic fermentation. 
Maltose, C.H»On + H,O, capable of the alcoholic fermenta- 
tion. The chief sugar of the digestive process. 
All the above are much less sweet and soluble than ordinary 
cane-sugar. 
2. THE StarcHEs: Glycogen, OsH1Os, convertible into dex- 
trose. Occurs abundantly in many foetal tissues and in the 
liver, especially of the adult animal. 
Dextrin, CsHy.O;, convertible into dextrose. Soluble in 
water; intermediate between starch and dextrose; a product 
of digestion. 
Pathological: Grape-sugar occurs in the urine in diabetes 
mellitus. 
Certain substances formed within the body may be regarded 
as chiefly waste-products, the result of metabolism or tissue- 
changes. 
They are divisible into nitrogenous metabolites and non- 
nitrogenous metabolites. 
Nitrogenous Metabolites. 
1. Urea, uric acid and compounds, kreatinin, xanthin, hypo- 
xanthin (sarkin), hippuric acid, all occurring in urine. 
2. Leucin, tyrosin, taurocholic, and glycocholic acids, which 
occur in the digestive tract. 
