FATS, PHOSPHATIDS, ETC. 87 



vegetable fats, notably in palm oil, whence it derives its name. 

 It predominates in human fat. It melts first at about 50, re- 

 solidifies, and melts again at about 66. 



Triolein, or olein, is found in animal, and to a greater extent 

 in vegetable fats and oils. It melts at 6 C, and is thus a 

 liquid (an oil) at room temperature. The presence of olein 

 lowers the melting point of natural fats. If exposed to the air 

 olein quickly becomes rancid. Oleic acid, by reason of its 

 double bond will take up iodine as described above. 



Butter. Butter, the fat obtained from cream, contains about 

 85% fats. About 1% of this is made of lower fatty acids. Of 

 the remainder 60-70% is palmitin, and 30-40% olein. Butter 

 contains very little stearin. 



Oleomargarine is made usually from beef fat. The fat is 

 melted, cooled, the oily portion pressed out and this mixed with 

 various substances such as peanut oil, lard, etc., and finally 

 churned up with milk to give it a butter flavor. If oleomarga- 

 rine is made from clean, wholesome materials it is a perfectly sat- 

 isfactory food substance. It often lacks certain substances 

 found in butter, however, which are called vitamines, which 

 recently have been shown to be very valuable materials to the 

 body. Cod liver oil also contains these substances. Perhaps 

 this fact justifies the popular impression of its beneficial nature. 



Lanolin, or wool fat, which is an ester of higher fatty acids 

 chiefly with the alcohol cholesterol in place of glycerine, is use- 

 ful in medicine. It forms extremely fine emulsions and thus 

 serves as a valuable basis for the formation of salves and oint- 

 ments. Substances containing alcohols other than glycerine, 

 such as cholesterol are often classed as waxes. 



Phosphatids, Cerebrosides, and Sterols 



A large number of substances have been isolated from 

 animal and plant tissues which have certain similarities to 

 the fats, such as solubilities, general appearance, etc. Some 

 of these compounds are also related chemically to the 

 fats. Substances of this nature are found in all cells, both 



