THE FATS. 75 



Bitches which are fed solely on lean meats continue to furnish milk 

 containing an abundance of butter. Pettenkoffer and Yoit further 

 showed in dogs that when the carbohydrates remained constant, but 

 the albuminous food was increased, a steady gain in fat occurred, as 

 shown in the table : 



CE in geIt d ed ateS Meat ingested. Gain in fat. 

 379 grams. 211 grams. 24 grams 



379 " 608 " 55 " 



379 " 1469 " 112 " 



A further illustration is had in the transformation of the muscular 

 tissue of cadavers into so-called adipocere, a substance which con- 

 sists to the extent of 97 per cent, of ammonium palmitate with a 

 small amount of stearate. 



Under various pathologic conditions, finally, we can follow with 

 the microscope the gradual transformation of albuminous material 

 into fat. 



All fats consist of carbon, hydrogen, and oxygen. They are 

 insoluble in water, slightly soluble in cold alcohol, while in hot 

 alcohol, ether, and benzol they dissolve with ease. Chemically 

 speaking, they are neutral esters which are formed through the union 

 of an acid with an alcohol according to the equation : 



C 2 H 6 .OH -f CH 3 .COOH = CH 3 .COO.C 2 H 5 + H 2 O. 



The fats which are principally found in the animal world, viz., 

 palmitin, stearin, and olein, similarly result through the union of 

 their respective monobasic acids with the triatomic alcohol glycerin. 

 This union is effected as shown in the equations : 



C 3 H 5 (OH) 3 + 3C v H a .COOH = C 3 H 5 (C 16 H 31 O 2 ) 3 + 3H 2 O 

 Glycerin. Palmitic acid. Palmitin. 



C 3 H 5 (OH) 3 + 3C, 7 H ? , 5 .COOH = C 3 H 6 (C 18 H 35 O 2 ) 3 + 3H 2 O 

 Stearic acid. Stearin. 



C 3 H 5 (OH) 3 + 3C 17 H 33 .COOH = C 3 H 5 (C 18 H 33 O 2 ) 3 + 3H 2 O 

 Oleic acid. Olein. 



They are thus triglycerides, and are accordingly termed tripal- 

 mitin, tristearin, and triolein. Other fats have also been found in 

 the animal world, but are of secondary importance. Such fats are 

 the so-called cetin (the palmitic acid ester of cetyl alcohol), which is 

 obtained from certain whales, the myricin of beeswax (the palmitic 

 acid ester of myricyl alcohol), etc. 



The animal fat as a whole usually represents a mixture of the 

 three triglycerides, palmitin, stearin, and olein, in variable propor- 

 tions, the stearin predominating in the more solid varieties, while 

 olein prevails in the more liquid fats. In human fat olein represents 

 about 670 to 800 pro mille of the total amount. 



The triglycerides are lighter than water; they are soluble in 

 benzol and ether, and in hot alcohol, while in water and cold 



