184 



W. K. BLOOR 



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

 to other sources (Bloor (i), 120; Leathes (c), 1910). 



The Lipoids 



Naturally occurring compounds of the fatty acids, together witl 

 certain substances found naturally in chemical association with them. 



The group is characterized in general by insolubility in water anc 

 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 liquit 

 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 anc 

 nitrogen. Lecithin, cephalin, etc. 



Glycolipoids. Compounds of the fatty acids with a carbohydrate anc 

 nitrogen but containing no phosphoric acid. Cerebron. 



{Amino lipoids, Sulpho lipoids, etc. Various groups which may 

 added as soon as they are sufficiently well characterized.) 



Derived Lipoids. Substances, derived from the above groups 

 splitting, which have the general properties of the lipoids. 



Fatty acids of various series. 



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

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

 Cetyl alcohol (C 16 H 33 OH), myricyl alcohol (C 30 H 61 OH), cholestei 

 (C 27 H 43 OH). 



Simple Lipoids. The Fats. Esters of the triatomic alcohol glycerol 

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

 tures and 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, thej 

 are triatomic esters, i. e., all three of the hydroxyl groups of the alcohc 

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

 sionally found but usually only where metabolic processes are in active 

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

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

 same producing simple glycerides or may be different, producing mixec 

 glyeerides. As the knowledge of the chemistry of the fats increases 

 becomes evident that mixed glycerides are of much more frequent 

 currenco than was previously supposed a fact which is of considerable 



