288 INTERNAL SECRETION 



stearate and cholesterin palmitate in a state of chemical purity. 

 They obtained, further, the phosphatide, sphingomyelin, and the 

 non-phosphoric galactocide, phrenosin. The phrenosin was 

 identified by polarimetric estimation of the galactose obtained 

 after hydrolysis. Free cholesterin was carefully \vatched 

 for, but was not found to be present. Even with Windau's 

 extremely sensitive digitonin reaction, free cholesterin could not 

 be detected in either the hot or cold acetone extract of suprarenal. 

 These authors lay stress upon the fact that their results do not 

 support Powell White's assumption, that the double refractive 

 substances of the suprarenal consist of a mixture of free cholesterin 

 and fatty acids. On the contrary, the results of these experiments 

 confirm another view held by Powell White, to the effect, namely, 

 that the pure cholesterinesters do not yield double refractive 

 granules, but that when in combination with fatty acids, the 

 granules which they yield are double refractive. Seeing that the 

 presence under physiological conditions of true cholesterinesters 

 in the organism is denied by Biinz, Tebb, and by Moore, this 

 account of cholesterin palmitate and cholesterin stearate in the 

 suprarenal is very remarkable. 



According to Rosenheim and Tebb, the double refractive sub- 

 stances of the suprarenal consist of a mixture of free stearic and 

 other fatty acids, together with a small proportion of sphingo- 

 myelin. 



In his review of the morphology of the lipoicl substances (1909), 

 Aschoff affirms, upon the ground of results yielded by his own 

 experiments, that the following bodies may show double refractive 

 myelin forms, and, occasionally, globules : 



(1) The phosphatides, including lecithin, though the latter is 

 difficult to obtain in a state of chemical purity. 



(2) The soaps of the oleic acids. 



(3) The cholesterinesters. 



(4) Solutions of cholesterin in the phosphatides, in the oleic 

 acids, and the fats. 



(5) Solutions of the cholesterinesters in the fats (perhaps also 

 in the phosphatides, though, up to now, this has not been tested). 



Of the double refractive substances included in these five 

 classes, the cholesterinesters alone constantly and readily yield 

 permanent emulsions of double refractive globules. The sub- 

 stances in classes i and 2 frequently yield transient accidental 

 globule formations with double refractivity, but the results cannot 

 be relied upon. The substances in classes 4 and 5, on the other 

 hand, invariably yield emulsions containing globules, but these 

 are either not double refractive, or there is coarse crystalline pre- 

 cipitation of the globules without typical crystalline formation. 

 In all essentials, then, the double refractive substance is repre- 

 sented by the cholesterinesters. 



In regard to the colour reactions of the cholesterinesters, 



