FATS. 63 



when a large quantity is used, it unites with the fatty acid. 

 The process of formation of glycerine and fatty acids in- 

 volves the fixation of a certain quantity of water ; so that 

 the combined weights of the glycerine and acid exceed that 

 of the fat originally employed. 1 It is thought by some that 

 this acidification of fat takes place to a certain extent in di- 

 gestion ; however this may be, it is not an essential part of 

 the digestive process. 



Emulsion. When liquid fat is violently shaken up with 

 water, it is minutely subdivided, and an opaque milky mix- 

 ture is the result. But this is momentary, the two liquids 

 separating almost immediately from each other when they 

 are no longer agitated. There are certain fluids, however, 

 which have the property of holding fat permanently in a 

 state of minute subdivision and suspension, forming what is 

 called an emulsion. Out of the body, mucilaginous fluids 

 and white of egg have this property. In the body, we find 

 as examples of emulsions the chyle, which is formed by the 

 action of the pancreatic juice upon the fatty elements of 

 food, and milk, which is composed of butter held in suspen- 

 sion by the water and caseine. The property of forming 

 emulsions with certain liquids is one of the most interesting 

 attributes of the fats, as it is in this form only that it can 

 find its way from the alimentary canal into the general 

 system. 



Origin and Functions of Fat. One source of fat in the 

 economy is the food. It constitutes an important article of 

 diet, existing in animal food in the form of adipose tissue, 

 and mingled to a certain extent with the muscular tissue. 

 Vegetable oil also is quite a common article of food. When 

 introduced in the form of adipose tissue, the fat is freed from 

 its vesicles by the action of the gastric juice, is generally 



1 REGNAULT, Cours EUmentaire de Chimie, Paris, 1853, tome iv., p. 414. 



