226 ANIMAL FATS AND PHOSPHATIDES. 



have been found in many plant fats. The extent to which traces of 

 these oxyacids occur in the animal kingdom has not been thoroughly 

 investigated, but the occurrence of monoxystearic acid seems to have 

 been proven. 1 The occurrence of high molecular alcohols, although 

 ordinarily only in small amounts, has on the contrary been positively 

 shown in animal fat. 



The animal fats are of the greatest interest and consist of a mixture of 

 varying quantities of TRISTEARIN, TRIPALMITIN, and TRIOLEIN, having 

 an average elementary composition of C 76.5, H 12.0, and O 11.5 per 

 cent. It must be remarked that in animal fat (mutton and beef tallow) 

 as well as in plant fat (olive-oil) mixed triglycerides, such as dipalmityl- 

 olein distearyl-palmitin and distearyl-olein, occur, and that these mixed 

 glycerides may also be prepared synthetically. 2 



Fats from different species of animals, and even from different parts 

 of the same animal, have an essentially different consistency, depending 

 upon the relative amounts of the different individual fats present. In 

 solid fats as tallow tristearin and tripalmitin are in excess, while 

 the less solid fats are characterized by a greater abundance of triolein. 

 This last-mentioned fat is found in greater quantities proportionally 

 in cold-blooded animals, and this accounts for the fact that the fat of 

 these animals remains fluid at temperatures at which the fat of warm- 

 blooded animals solidifies. Human fat from different organs and tissues 

 contains, in full numbers, 67-85 per cent triolein. 3 The melting-point 

 of different fats depends upon the composition of the mixtures, and it 

 not only varies for fat from different tissues of the same animal, but also 

 for the fat from the same tissues in various kinds of animals. 4 



Neutral fats are colorless or yellowish, and, when perfectly pure, 

 odorless and tasteless. They are lighter than water, on which they 

 float when in a molten condition. They are insoluble in water, dissolve 

 in boiling alcohol, but separate on cooling often in crystals. They are 

 easily soluble in ether, benzene, chloroform, carbon disulphide and petro- 

 leum ether. The fluid neutral fats give an emulsion when shaken with 

 a solution of gum or albumin. With water alone they give an emulsion 

 only after vigorous and prolonged shaking, but the emulsion is not per- 



1 Erben, Zeitschr. f. physiol. Chem., 30; Bernert, Arch. f. exp. Path. u. Pharm., 49. 



2 Guth, Zeitschr. f. Biologie, 44; W. Hansen, Arch. f. Hygiene, 42; Holde and 

 Stange, Ber. d. d. chem. Gesellsch., 34; Kreis and Hafner, ibid., 36. 



3 See Knopfelmacher, " Untersuch. iiber das Fett im Sauglingsalter," etc., Jahrbuch 

 f. Kinderheilkunde (N. F.), 45, which also contains the older literature; Jaeckle, 

 Zeitschr. f. physiol. Chem., 36. 



4 According to Gilkin (Ber. d. d. chem. Gesellsch., 41) the fat from bone-marrow 

 and also other fats of animal and plant origin contain iron, which cannot be removed 

 by water containing hydrochloric acid. 



