SECT. 7] OF EMBRYONIC DEVELOPMENT 991 



very near the carbohydrate level can be calculated. This was first 

 pointed out by Needham in 1927, who suggested that these researches 

 could be interpreted as a progressive ehmination of leaks. 



17. Indirect evidence about the utilisation of protein by the em- 

 bryo can be gained from the work of Scheminzki, who determined 

 the resistance of the trout egg to damage by electric currents during its 

 development. The whole period was 55 days, and for the first 30 days 

 there was practically no change in the resistance, but after that time it 

 rose tremendously, the strength of current required to produce precipi- 

 tation of the ichthulin in one minute increasing six times in the last 

 25 days of development. The effect of the current was to render the 

 egg-membrane permeable to cations, which diffuse out and cause the 

 ichthulin to be precipitated. Jarisch showed that lipoids and fats in 

 systems poor in salt favour the precipitation of globulin, so if the 

 current dismisses the cations from the egg, the precipitation of ichthulin 

 will be more favoured the more fatty substances there are present. 

 Scheminzki's curve becomes, then, in some measure an index of the 

 amount of fat absorbed by the embryo, and the fact that it is of so 

 gradual a slope during the first two-thirds of development may be 

 interpreted as showing a greater intensity of fat absorption (and 

 combustion?) towards the end of development than towards the 

 beginning. These findings may be compared with those of Gage & 

 Gage on the chick embryo. 



18. Besides Tomita and Grafe, a few other investigators drew 

 attention in the past to evidence showing that fat was not the only 

 energy source of the chick embryo. Droge considered that protein 

 must take a share in the work, and Sakuragi specifically went into 

 the question of the other energy sources of the embryo. In the 

 German summary to his Japanese paper, he says, "Obwohl bisherige 

 Autoren, welche sich mit Stoff- und Energiewechsel von bebriitenden 

 Hiihnereiern beschaftigen, die Bedeutung des Kohlehydrates fur 

 Energiewechsel ganz vernachlassigten, glaubt der Verfasser, dass der 

 schon vorhandene Traubenzucker in den ersten Bebrutungstadien 

 besondere Wichtigkeit und grosse Bedeutung dafur hat, und dass der 

 erste chemische Vorgang in den bebriitenden Eiern in der Zersetzung 

 von Traubenzucker besteht". Sakuragi estimated the free and com- 

 bined sugar, the fat, the various fractions of nitrogen, and the 

 glycogen at the different stages of development, and interpreted his 

 figures as showing that throughout development carbohydrate was 



