THE METABOLIC GRADIENTS OF VERTEBRATE 

 EMBRYOS. I. TELEOST EMBRYOS. 



LIBBIE H. HYMAN, 

 HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



I. INTRODUCTION. 



The present paper is a record of observations on the disintegra- 

 tion gradients of some teleost embryos. Since these gradients 

 have served to explain much that was formerly obscure in the 

 physiology and development of organisms, it has seemed to us 

 worth while to study them in as wide a range of living forms, 

 both adult and embryonic, as practicable. In particular it has 

 seemed desirable to determine the susceptibility gradients in the 

 vertebrates in order to analyze their role in normal and terato- 

 logical development and in the physiology of at least certain 

 systems. 1 Since it is impracticable to study adult vertebrates by 

 the susceptibility method owing to the difficulty of determining 

 the time of death of different regions, our attention has been 

 necessarily confined to embryonic stages. The recent publication 

 of Bellamy ('19) on the frog represents the first of these in- 

 vestigations on the vertebrate embryo. In this paper Bellamy 

 described the disintegration gradients of the frog at various stages 

 of development and showed that the teratological forms experi- 

 mentally produced by him and by a number of previous investiga- 

 tors can be easily and simply accounted for on the basis of these 

 gradients. Similarly in these papers I shall describe the disin- 

 tegration gradients of other vertebrate embryos and attempt to 

 correlate them with well-known facts of normal and teratological 

 development. 



When an organism is exposed to a lethal concentration of a 

 toxic solution, it is found that all of its parts do not die simul- 



1 In particular the gradients have been of great service in interpreting the 

 physiology of the nervous system, the digestive system, and the heart. 



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