286 INTERNAL SECRETION 



substance increases, while the fat is reduced in proportion. Where 

 muscular exertion is prolonged to fatigue, the double refractive 

 substance disappears, and the fat spreads through the whole of 

 the cortex. The authors point out, however, that these substances 

 may neither of them represent the most important general product 

 of the secretory activity of the cortex, for they may be absent in 

 certain species, as in the case of the sheep. The brown pigment- 

 granules are specific to the suprarenal cortex of guinea-pigs. 

 These accumulate during repose and disappear very rapidly 

 during exhausting muscular exertion, fat being formed in the 

 cytoplasm in their place. 



These authors give no account of the chemical nature of the 

 double-refractive substance ; but they point out that it cannot be 

 identical with fat, and they think that its refractive power probably 

 points to myelin in combination with lecithin. 



As we have seen, this double-refractive lipoid substance was 

 almost invariably believed to be lecithin. The assumption was 

 justified by Virchow's discovery, as early as 1857, of the presence 

 of a substance which he described as myelin (medullary) in the 

 suprarenal, and which, from its chemical nature, he identified 

 with the substance which Gobley described as lecithin. A little 

 later, Bennecke pointed out that cholesterin, in combination with 

 a peculiar substance of fatty nature, plays the chief part in the 

 formation of myelin substances. But the peculiar richness in 

 lecithin of the suprarenals was again emphasized by Alexander. 

 He obtained his exceptionally high figures by multiplying by 8.8, 

 the phosphorus contents of the etheric extract of suprarenal. The 

 brothers Marino-Zucco, as well as Guarneri and Marino-Zucco, 

 obtained neurin and glycerite of phosphoric acid from etheric 

 extract of suprarenal. Manasse obtained a body from the supra- 

 renals, the phosphorus contents of which were 4.44 per cent., and 

 which, after decomposition by means of acids, yielded a carbo- 

 hydrate. Manasse concludes that this lecithin-carbohydrate com- 

 bination is jecorin. . 



Orgler (1904) analysed the suprarenals with the object of 

 ascertaining if they contained a body resembling protagon. 

 Liebreich gave the name of protagon to a homogeneous substance 

 which he regarded as the matrix of the lipoids found in the 

 brain.* By means of alcoholic and etheric extraction, Orgler 



* Later on, protagon was erroneously regarded as a body chiefly com- 

 posed of cerebrin and lecithin, because it yielded, as the products of 

 decomposition, cerebrosides, which are free from phosphorus, and phospha- 

 tides. Cerebrin is a body containing CON, as yet not exactly denned; 

 while, from the results of Strecker and Diakonow's investigations, lecithin 

 was commonly regarded as di-stearyl-glycerinite of phosphoric-acid-cholin. 

 But Thudichum had already suggested, and it was afterwards proved by 

 Fraenkel, that saturated lecithins of this description do not exist; that afl 

 lecithins are unsaturated phosphatides ; and that Diakonow himself had 

 isolated the unsaturated oleic acids from his own lecithin. Thus the finding 

 of a saturated di-stearyl lecithin must be attributed to erroneous description 

 of the experiments on the part of the text-books. 



