2QO INTERNAL SECRETION 



On the other hand, as Aschoff justly points out, Ciaccio's 

 chemical tests cannot be regarded as of any very great value, 

 seeing that protagon does not exist as a chemical entity and that 

 pure lecithin is scarcely obtainable. The term lecithin is not 

 applicable to the lipoids of the suprarenal ; all that can be posi- 

 tively stated is, that they are lipoids, that like the medullary 

 substance of the nerves, treatment with chromates renders them 

 insoluble, and that they give a sudan reaction. From what has 

 been observed up to the present, it seems far more probable that 

 they are cholesterinesters and sphingomyelin. 



In my own researches into the nature of the so-called lipoid 

 substances, the material was provided by the suprarenals of 

 swine, while the method which I employed was an adaptation of 

 S. Fraenkel's method for fractional distillation of the lipoids of 

 the brain.* It must be explained, first of all, that the process 

 consists in extracting the different groups of lipoid substances 

 in such a manner as to separate the groups in the process of 

 extraction. The tissues are first dehydrated with cold acetone, 

 and are then successively subjected to the action of a number of 

 suitable organic solvents. By this means, the cholesterin group 

 is separated from that of the unsaturated phosphatides, and this 

 again from that of the saturated phosphatides and the sphingo- 

 galactosides. By weighing the extracts it is possible to ascertain, 

 not exactly, but approximately, the amount of the total lipoids 

 as well as that of the single lipoid groups, together with the 

 relationship which these bear to the total amount of lipoids. 



It has been shown by Fraenkel and his co-workers that every 

 organ contains lipoids which are, as a rule, characteristic of it; 

 and that the same organ, in different classes of animals, contains 

 phosphatides and lipoids which are also chemically differentiated. 

 The differentiation which exists between the lipoids of different 

 organs in different species on the other hand, is both qualitative 

 and quantitative. Finally, it must be borne in mind that, in spite of 

 their ready crystallinity, the lipoids which are normally present 

 in the tissues may not be demonstrable by histological tests, for 

 they may be present in a state of solution in one another. Under 

 pathological conditions, the breaking-up of such a state of in- 

 solution may cause the one or the other substance to appear. 



My experiments were conducted in the following manner : 

 Fresh pig's suprarenals were freed from the surrounding fat, cut 

 up in the mincing machine, dehydrated with plenty of cold 

 acetone, and then exhaustively distilled by means of boiling 

 acetone. The acetone extract contains the entire group of the 

 cholesterins, free cholesterin, cholesterinester, possibly also the 



* These experiments were carried out under S. Fraenkel's direction 

 in the laboratories of the L. Spiegler Institute in Vienna. A detailed 

 account, together with chemico-analytical results, will be published in the 

 " Biochemischen Zeitschrift." 



