CARBOHYDRATES, ACIDS, FATS, OILS 85 



117. Lecithins. — ^These are often called the phos- 

 phorized fats. It has previously been stated that neutral 

 fats are combinations of fatty acids and glycerin (glycerol). 

 Lecithins are compounds in which one of the radicals 

 of a fatty acid is replaced by a compound of phosphorus. 

 They are widely distributed in nature. They appear to 

 be an active component of every cell, both of vegetable 

 and animal tissue, and they are especially abundant in 

 seeds, in the nerve system, in fish, eggs, and in the yolk 

 of eggs. These compounds evidently fill an important 

 place in plant and animal nutrition. There are good 

 theoretical reasons for suggestiag that lecithins serve as 

 a stepping-stone to the synthesis of the nucleo-proteins. 

 In digestion they behave like the true fats. 



118. Enzyms, anti-bodies, hormones, vitamines 

 (accessories). — ^The science of nutrition must now deal 

 with a class of bodies which have not been isolated, some 

 of which have merely a theoretical standing, and all of 

 which are known chiefly by their reactions. 



Certain of these bodies are formed within the animal 

 organism and others are associated with foods. 



The subject of enzyms is treated in Par. 128. 



Anti-bodies are bodies which in some manner neu- 

 tralize or hinder the specific action of some other body, 

 as for instance the anti-enzyms. It is held that an anti- 

 pepsin exists in the mucous membranes of the stomach 

 and an anti-trypsin in the mucous membrane of the 

 intestine which render these linings immune to the 

 action of the digestive juices. 



Hormones, or "chemical messengers" are represented 

 by secretin (see Par. 161) which reacts upon certain 

 secretory glands, as for instance the pancreas, causing a 

 flow of the digestive fluid. The formation of secretin is 



