and Laboratory Methods. --4" 



GENERAL PHYSIOLOGY. 



RAYMOND PEARL, University of Michigan. 



Books and Papers for Review should be Sent to Raymond Pearl, Zoological Laboratory, 

 University of Michigan, Ann Arbor, Mich. 



_.,„„... T- •, J ^ The problem of the energy relations 



TangI, F. Beitrage zur Energetik der Onto- '^ °-' 



genese. I. Mitth. Die Entwicklungsarbeit involved in the various physiological 

 im Vogdei.^ Arch. f. d. ges. Physiol. 93: processes going on in the organism is 



one which has been given but com- 

 paratively little general attention by animal physiologists. Tangl has 

 undertaken the investigation of one phase of the problem, viz., the deter- 

 mination of the amount of energy involved in the processes of ontogenetic 

 development, and in this paper are contained his first results from the study 

 of birds' eggs. He calls the total amount of chemical energy which is 

 transformed during the development of the embryo the " Entwicklungsarbeit " 

 (work done in development), and proceeds to find by careful measurements what 

 the amount of this energy in a given case is. The principle of the method of 

 determining the " Entwicklungsarbeit " is as follows : The energy content of the 

 egg is determined at the beginning and at the end of development. Then the 

 difference in these two quantities indicates the amount of energy which has been 

 transformed and utilized in the development. As material the eggs of the spar- 

 row and of several varieties of hens were used. The experimental procedure in 

 the case of the sparrow eggs was as follows : An egg was first weighed and 

 measured ; then broken into a clean watch glass of known weight, and the em- 

 bryo measured. The eggs and shell were then dried in a vacuum at 50° — 60° 

 C. Thus the weight of the dry substance was obtained, and from this dry sub- 

 stance pastilles were made in a pastille press. These pastilles were then burned in 

 a Berthelot Mahler calorimetric bomb, and the energy content of the dry substance 

 obtained. The procedure when hen's eggs were used differed from this only in 

 minor details. It was found that in the complete development of the sparrow 

 embryo the work done amounted to 755 gram calories, or in mechanical units 

 3.16 X 10^ " ergs. For the development of the hen's egg up to the time of hatch- 

 ing 16 kilogram calories were used, or in mechanical units 66.9x10^'^ ergs. 

 In the complete development of each gram of the embryo 65S gram calories are 

 transformed, and for each gram of dry substance of the developed embryo 3426 

 calories of chemical energy have been transformed. It appeared very clearly in 

 the experiments that a considerably larger amount of energy was used in the 

 early stages of development than in the later stages. There is evidence in the 

 results that indicates that the energy necessary for development comes from the 

 transformation of the chemical energy of the fat in the egg. Measurements of 

 the energy content of different organ systems in the developed embryo showed 

 that the muscles had the highest specific energy content (66S7 calories) and the 

 bones the lowest (4907 calories). R. p. 



