SECTION III 

 THE FATS 



THESE substances are widely distributed throughout the animal and vege- 

 table kingdoms. In the higher animals they are the main constituents of 

 the fatty or adipose tissue lying under the skin and between the muscles, 

 and often forming large accumulations around the viscera. In the marrow 

 of bones they may amount to 96 per cent. They also occur in fine particles 

 distributed through the protoplasm of cells and probably also in combination 

 with the other constituents which make up protoplasm. Large amounts are 

 also found in certain members of the vegetable kingdom, as, for instance, 

 in the fatty seeds and nuts, e.g. linseed, olives, Brazil nuts. 



CHEMISTRY OF THE FATS 



The fats are esters of glycerol and the fatty acids. Glycerol is a trihydric 

 or triatomic alcohol and can therefore form esters with one, two, or three 

 of its hydroxyl groups ; thus with acetic acid the following compounds are 

 known : 



(1) (2) 



CH 2 OH CH 2 OH 



I I 



CHOH CH OC.CH 3 



I I 



CH 2 OC.CH 3 CH 2 OH 



a-monacetin /3-monacetin 



monoglycerides 



(3) (4) (5) 



CH 2 OC.CH 3 CH 2 OH CH 2 OC.CH 3 



I ' I I 



CHOH CH OC.CH 3 CH OC.CH 3 



I I I 



CH a OC.CH 3 CH 2 OC.CH 3 CH 2 OC.CH 3 



a, a diacetin a, /3 diacetin triacetin 



x .- ' triglyceride 



diglycendea 



In these compounds the phenomenon of isomerism occurs owing to the 

 presence of primary and secondary alcohol groups in glycerol. In the case 



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