42 VETERINARY PHYSIOLOGY 



The most abundant fatty acids of the body are : — 



^^tnr.tpH f P^l^^itic ^^''^> C,,H3,C0C)H ; 

 t5aturatea ^g^^^^^^ ^^-^^ C17H35COOH ; 



Unsaturated — Oleic Acid, C17H33COOH ; 



The unsaturated acids are more readily oxidised than the 

 saturated. They tend to break at the double link ia the 

 chain thus — 



H H H H 



-C— C=C— C- 



I 



H 

 The three fats are — 



H 



Palmitin, C3H,(O.C,5H3iCO)3 = C.^H^gOe, 

 Stearin, C3H5(O.Ci7H35CO)3 = CUH^ioOe, 

 Olein, C3H,(O.C\,H33CO)3 = C„H,o A- 



It will be observed that the molecules of these fats are 

 very rich in carbon and hydrogen, and very 2^oor in 

 oxygen, containing only about 12 per cent., i.e. they contain 

 a large amount of material capable of being oxidised, and 

 thus capable of affording energy in the process of combustion. 



The fats resemble one another in being insoluble in 

 water, but soluble in ether and in hot alcohol. As the 

 alcohol cools, they separate out as crystals. They differ 

 from one another in their melting point, palmitin melting at 

 the highest and olein at the lowest temperature. Fat which 

 is rich in palmitin and stearin, as ox fat, is thus hard and 

 solid at the ordinary temperature of the air, while fat rich in 

 olein, as dog fat, is semi-fluid at the same temperature. 

 Olein acts as a solvent for the fats of a higher melting 

 point. (For tests, see Chemical Physiology.) 



The functions of adipose tissue are twofold : — 



1st. Mechanical. — The mass of adipose tissue under the 

 skin is of importance in protecting the deeper structures 

 from injury. It is a cushion on which external violence 

 expends itself Further, this layer of subcutaneous fat 



