FATS. 133 



and myristin may occur abundantly in plant organisms. The gen- 

 erally accepted system of nomenclature for these fats is to apply 

 the prefix " tri " in each case (e. g., /n-palmitin) since three fatty 

 acid radicals are contained in the neutral fat molecule. 



Fats occur ordinarily as mixtures of several individual fats. 

 For example, the fat found in animal tissues is a mixture of tri- 

 olein, tri-palmitin and tri-stearin, the percentage of any one of 

 these fats present depending upon the particular species of animal 

 from whose tissue the fat was derived. Thus the ordinary mutton 

 fat contains more tri-stearin and less tri-olein than the pork fat. 

 Human fat contains from 67 per cent to 85 per cent of tri-olein 

 and according to Benedict and Osterberg, upon analysis yields 

 76.08 per cent of carbon and 11.78 per cent of hydrogen. 



Pure neutral fats are odorless, tasteless and generally colorless. 

 They are insoluble in the ordinary protein solvents such as water, 

 salt solutions and dilute acids and alkalis but are very readily 

 soluble in ether, benzene, chloroform and boiling alcohol. The 

 neutral fats are non-volatile substances possessing a neutral reac- 

 tion. If allowed to remain in contact with the air for a sufficient 

 length of time they become yellow in color, assume an acid reaction 

 and are said to be rancid. The neutral fats may be crystallized, 

 some of them with great facility. The crystalline forms of some 

 of the more common fats are reproduced in Figs. 35, 36 and 37 

 on pages 131, 134 and 136. Each individual fat possesses a specific 

 melting- or boiling-point (according to whether the body is solid 

 or fluid in character) and this property of melting or boiling at a 

 definite temperature may be used as a means of differentiation in 

 the same way as the coagulation temperature (see page 242) is 

 used for the differentiation of coagulable proteins. When shaken 

 with water, or a solution of albumin, soap, or acacia, the liquid 

 fats are finely divided and assume a condition known as an emul- 

 sion. The emulsion with water is transitory, while the emulsions 

 with soap, acacia, or albumin, are permanent. 



The fat ingested continues essentially unaltered until it reaches 

 the intestines where it is acted upon by pancreatic lipase (steapsin) 

 the fat-splitting enzyme of the pancreatic juice (see page 143), 

 and glycerol and fatty acid are formed from a large portion of 

 the fat. Part of the fatty acid thus formed is dissolved in the 

 bile and absorbed while the remainder unites with the alkalis of 

 the pancreatic juice and forms soluble soaps. These soaps may 

 further act to produce an emulsion of the remaining fat and thus 



