SECT. 6] 



OF THE EMBRYO 



915 



the data which have been accumulated for the chick. It is possible 

 to construct, from the analyses of FehHng and others on man, Michel 

 on the rabbit, Liesenfeld on the dog and Hayes on the salmon, a 

 table showing the percentage composition of the embryo, and, when 



Rabbit 



embryo 

 constitution 

 sAsh ] 



o Protein fehling ^ 

 • Fat J 

 D Protein] 



■ Fat JFriedenthal 

 EiAsh J 



Days concepfci 



^ 5 



Dog Embryo Consbibution ^^^ 



Liesenfeld, DahmenSiJunkersdorf • 



Costantino ♦ 



Fig. 246. 



20 30 40 50 

 Days conception age 



Fig. 247. 



the data are plotted on a graph, Figs. 245, 246, 247 and 248 are 

 obtained. Total carbohydrate cannot be considered, for the chick 

 is the only embryo in which this has so far been estimated, and, 

 in any case, it does not form a large part of the total solid there. 

 But it is clear that both in 

 the case of the human and the 

 rabbit embryo there is just 

 that cross-over between pro- 

 tein and fat which we find so 

 markedly in the chick em- 

 bryo. It is interesting that 

 this was not noticed by the 

 workers themselves, because 

 they did not express their re- 

 sults in percentage dry weight, 

 and all these inter-relations 

 are, of course, obscured, if 

 percentage wet weight is alone taken into consideration, owing to 

 the sharply decreasing water-content. Next it is to be observed that 

 Table 108 demonstrates a distinct lowering of the ash-content in 

 grams per cent, during the development of the chick — this was the 

 discovery of Murray — but the figures plotted in Figs. 245 and 246 do 



10 20 30 W 50 60 70 30 40 50 60 70 80 90 100 110 120 

 -" — Days — ► 



Fig. 248. 



