ENERGY OF DEVELOPMENT 491 



Energy of Development. 



Interesting observations have been made ol" the anioinit of 

 energy used by a develojjing organism. Tangl determined the 

 energy content of fresh laid eggs and compared that amount with 

 the energy value of the embryo and yolk found in the shell at 

 the moment of hatching. He reported that each gram of chick 

 liad been formed at the cost of the energy represented by 058 small 

 calories. 



l^'urther, 35 per cent. (32 Calories) of the total chemical energy 

 of the fresh egg is deposited in the tissues of the young embryo ; 

 48 per cent. (44 Calories) is found to a large extent in the abdomen 

 of the chick as a store of potential energy to be drawn upon during 

 early life ; while the balance — 17 per cent. (16 Calories) — has been 

 spent in the development of the chick. That is, about one-sixth 

 of the total energy of a lien's egg is required for the work of 

 elaboration of the tissues of the chick, which tissues contain one- 

 third of the original energy of the egg. 



