CHEMIC COMPOSITION OF THE HUMAN BODY. 13 



THE FATS. 



The fats constitute a group of organic bodies found in the tissues of both 

 vegetables and animals. In the vegetable world they are largely found in 

 fruits, seeds, and nuts, where they probably originate from a transformation 

 of the carbohydrates. In the animal body the fats are found largely in the 

 subcutaneous tissue, in the marrow of bones, in and around various internal 

 organs and in milk. In these situations fat is contained in small, round or 

 polygon-shaped vesicles, which are united by areolar tissue and surrounded 

 by blood-vessels. At the temperature of the body the fat is liquid, but after 

 death it soon solidifies from the loss of heat. 



The fats are compounds consisting of carbon, hydrogen, and oxygen. 

 The percentage composition of fat (stearin) is as follows: carbon 76.86, hy- 

 drogen 12.36 oxygen 10.78. The fat, as found in animals, is a mixture, in 

 varying proportions in different animals, of three neutral fats stearin, pal- 

 mitin, and olein. Each fat is a derivative of glycerin and the particular acid 

 indicated by its name e. g., stearic acid, in the case of stearin, etc. The re- 

 action which takes place in the combination of glycerin and the acid is ex- 

 pressed in the following equation: 



Glycerin. Stearic Acid. Stearin. Water. 



Hence, strictly speaking, the fats are compound ethers, in which the 

 hydrogen of the organic acid is replaced by the trivalent radicle, tritenyl, 

 C 3 H 6 . 



Stearin, C 3 H 6 (C 18 H 35 O 2 ) 3 , is the chief constituent of the more solid fats. 

 It is solid at ordinary temperatures, melting at 55 C., then solidifying again 

 as the temperature rises, until at 71 C. it melts permanently. It crystal- 

 lizes in square tables. 



Palmitin, C 3 H 6 (C 16 H 31 O 2 ) 3 , is a semifluid fat, solid at 45 C. and melting 

 at 62 C. It crystallizes in fine needles, and is soluble in ether. 



Olein, C 3 H 6 (C 18 H 33 O 2 ) 3 , is a colorless, transparent fluid, liquid at ordi- 

 nary temperatures, only solidifying at o C. It possesses marked solvent 

 powers, and holds stearin and palmitin in solution at the temperature of 

 the body. 



Saponification. When subjected to the acton of superheated steam, 

 a neutral fat is saponified i. e. t decomposed into glycerin and the particular 

 acid indicated by the name of the fat used: e.g., stearic, palmitic, or oleic. 

 The reaction is expressed as follows: 



Olein. Water. Glycerin. Oleic Acid. 



