THE REPRODUCTIVE GLANDS. 451 



Of the mineral constituents, the large amount of calcium and 

 phosphoric acid is especially noteworthy. Soluble phosphates, 

 however, are not found as such in the yolk. The amount of potas- 

 sium and sodium, it- will be observed, is much smaller than in the 

 albumen. 



The Albumins. Our knowledge of the individual albumins which 

 are found in the yolk is still very imperfect. But it appears from 

 recent researches that they are represented notably by nucleo- albu- 

 mins, which in turn may be combined with lecithins to form com- 

 plex lecithalbumins. This, however, is not proved, and it is as- 

 sumed by some that the lecithins which are obtained so commonly 

 together with the albumins do not exist in chemical combination, 

 but are to be regarded as contaminations. The best known repre- 

 sentative of the nucleo-albumins of the yolk is the so-called ovo- 

 vitellin. True nucleins do not occur in the yolk. 



Ovovitellin. Formerly this was regarded as a globulin, but it is 

 now known to be a nucleo-albumin in which an albuminous radicle 

 is combined with a paranuclein i. e., a nuclein which does not yield 

 nucleinic bases on decomposition with mineral acids. The substance 

 has thus far not been obtained free from lecithins, and it is for this 

 reason that the latter is thought by some to be present in chemical 

 combination. 



Of the character of the albuminous radicle which is present 

 in combination with the paranuclein nothing is known. The 

 paranuclein has recently been studied in detail by Levene and 

 Alsberg. They term it avivitellinic acid, and give the following 

 figures to express its elementary composition: C, 32.31; H, 5.58; 

 N, 13.13; P, 9.88; S, 0.3266; O, 38.28 per cent. In addition 

 they found 0.57 per cent, of iron, which is present in organic com- 

 bination. This is especially interesting in view of the fact that 

 Bunge also obtained a nuclein from the yolk of hens' eggs, which 

 contained iron, and which he termed hcematogen, as the product must 

 of necessity be concerned in the formation of the blood-coloring mat- 

 ter of the developing animal. The elementary composition of Bunge's 

 haBmatogen, however, is different from Levene's avivitellinic acid, 

 viz., C, 42.11; H, 6.08; 1ST, 14.73; S, 0.55; P, 5.19; Fe, 0.29 ; 

 and O, 31.05 per cent. Its relation to ovovitellin is at present 

 not clear, but it is manifestly closely related to avivitellinic acid. 



The albuminous radicle of avivitellinic acid manifestly contains 

 the protamin group, as Levene was able to isolate both arginin and 

 histidin from its decomposition-products, which resulted on boiling 

 the substance for seventy-two hours with a 20 per cent, solution of 

 hydrochloric acid. Whether or not lysin is also present remains to 

 be seen. The amount of arginin and histidin obtained was so small, 

 however, that it is scarcely warrantable to assume that a protamin 

 constitutes the entire albuminous radicle, as in the case of the nu- 

 cleins which can be obtained from certain fishes. The substance 

 gives Millon's reaction, moreover, which is not obtained with pro- 



