184 W. R. BLOOR 



discussion of the classification and of the members the reader is referred 

 to other sources (Bloor (i), 11)50; Leathes (c), 1910). 



The Lipoids 



Xatu rally occurring compounds of the fatty acids, together with 

 certain substances found naturally in chemical association with them. 



The group is characterized in general by insolubility in water and 

 solubility in "fat solvents," chloroform, benzol, etc. 



Simple Lipoids. Esters of the fatty acids with various alcohols. 



Fats. Esters of the fatty acids with glycerol. (Fats which are liquid 

 at ordinary temperatures are called oils.) 



]}'a.res. Esters of the fatty acids with alcohols other than glycerol. 

 Beeswax, lanolin, cholesterol oleate. 



Compound Lipoids. Compounds of the fatty acids with alcohols but 

 containing- other groups in addition to the alcohol. 



Phospholipoids. Substituted fats containing- phosphoric acid and 

 nitrogen. Lecithin, cephalin, etc. 



Glycolipoids.- Compounds of the fatty acids with a carbohydrate and 

 nitrogen but containing no phosphoric acid. Cerebron. 



(Amino lipoids, Sulpho lipoids, etc. Various groups which may be 

 added as soon as they are sufficiently well characterized.) 



Derived Lipoids. Substances, derived from the above groups by 

 splitting, which have the general properties of the lipoids. 



Fatty acids of various series. 



Sterols. Alcohols, mostly large molecular solids, found naturally in 

 combination with the fatty acids and which are soluble in ''fat solvents." 

 Cetyl alcohol (C 16 H 3 ,OHj, myricyl alcohol (C 30 H 01 Oil), cholesterol 



Simple Lipoids.- The Fats. Esters of the triatoinic alcohol glycerol. 

 They are commonly called fats when they are solid at ordinary tempera- 

 tures am! oils when liquid. Of the lipoids these are the most widely 

 distributed in .nature, the most important from the point of view of nu- 

 trition and the best understood chemically. As ordinarily occurring, they 

 are triatoniie esters, i. e., all three of the hydroxyi groups of the alcohol 

 are replaced by fatty acids. Diatomic and mouatomic esters are occa- 

 sionally found but usually only where metabolic processes are in active 

 progress as in germinating seeds and during fat digestion. The fatty 

 acids in combination with a single glycerin molecule may be either all the 

 same producing simple glycerides or may be different, producing mixed 

 glycerides. As the knowledge of the chemistry of the fats increases it 

 becomes evident that mixed glycerides are of much more frequent oc- 

 currence than was previously supposed a fact which is of considerable 



