NITROGENOUS EXTRACTIVES 



1 147 



contains as much as the embryo. The graph accordingly resembles 

 that for glycogen, for it is of the type in which the total amount of 

 the substance increases, while the amount of the substance outside 

 the embryo first increases and then decreases. Probably the reason 

 why the yolk has so much is that the yolk-sac and its vessels were 

 included in the analysis, and consequently the purine bases from the 

 nucleoprotein of their cells were 

 included. Mendel & Leaven- 

 worth have also estimated the 

 purines in the avian egg, and 

 their figures, which appear in 

 Fig. 343, agree with Sendju's as 

 demonstrating a vigorous syn- 

 thesis, although in absolute value 

 they much exceed his, by 22-0 to 

 7'0 on the last day of develop- 

 ment. This is due to the fact 

 that Mendel & Leavenworth 

 probably included the uric acid 

 present. 



Mendel & Leavenworth sepa- 

 rated a number of the individual 

 bases by the Kruger-Schmid pro- 

 cess, with the results shown in Fig. 344. Kossel's original figures are 

 placed beside them for comparison. The concentration of the bases 

 in the embryonic tissue was, it seemed, about the same as in adult 

 tissue, thus: 



Grams % wet weight 



Mendel 8c Leavenworth 

 © Guanine "j 



e Adenine >WhoU 



® HypoxanbhineJ 



Kosse 

 O Guanine 1 



O HypoxanbhineJ 



Days -* 5 



Fig. 344. 



Wells & Corper remarked in 1909 that foetal tissues seemed to con- 

 tain much more guanine than adenine, since on autolvsis they gave 

 twice as much xanthine as hypoxanthine. No more recent investi- 

 gations have been made exactly along these lines, but Calvery has 

 reported the presence of pentose nucleic acid with its pyrimidine, 



