FATS, PHOSPHATIDS, AND ALLIED SUBSTANCES 69 



80% 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 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. t 



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. 



Lecinthin and Cholesterol 



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 

 animal and vegetable, and particularly in the brain and nerve 

 tissues. Little is known of the biological function of these com- 

 pounds, although as our information increases, they appear to 

 be increasingly important. The composition of some of them 

 is known, whereas in the case of others, we have no assurance 

 that the substances reported are single compounds and not mix- 

 tures of closely related compounds. 



Lecithin. Lecithin, classed as a phosphatid, is one of the 

 interesting compounds of this type. It is found in all cells, in 

 greatest amount in egg yolk which contains about 10%. 



