610 



Ontogeny of Endocrine Correlation 



the analysis of the problem, to ascertain at 

 what stage in ontogeny (during either the 

 later prenatal or the early postnatal stages) 

 a temporary decrease in liver glycogen and 

 an increase in blood sugar can be produced 

 by adrenaline injection and whether such 

 changes can be prevented by insulin injection. 



of enzymes involved in glucose metabolism 

 (for a comprehensive treatment of the subject 

 see Cori, '46, and Young, '48). 



To sum up this account, it is at once 

 apparent that the problem of unravelling the 

 sequence of events leading to the establish- 

 ment of hormonal mechanisms which con- 



Fig. 213. Chart depicting manifold correlations in development of humoral activity in the chick embryo 



(after WiUier, '54). 



In any comprehensive attack on the over- 

 all problem consideration shovxld also be 

 given to the time in the course of development 

 when the many enzymes concerned with 

 carbohydrate metabolism become active, es- 

 pecially in the liver and skeletal muscle, and 

 also to whether the activity of such enzymes, 

 once established, can be influenced by hor- 

 mones. A pertinent clue may be taken from 

 the work of Cori and collaborators (see 

 Colowick et al., '47), who in an investigation 

 of the effects of hormones on enzymatic re- 

 action in vitro showed that insulin, and hor- 

 mones of the anterior pituitary (A.P.E.) and 

 adrenal cortex, have an influence on the 

 activity of hexokinase, the first of a chain 



tribute to the homeostatic regulation of blood 

 sugar is unusually complex. As may be seen 

 from the accompanying chart (Fig. 213), 

 three main periods or phases in the time 

 scale of the development of humoral activity 

 in the chick embryo may be recognized 

 (Willier, '54). 



The phase of independent functional ac- 

 tivity, extending roughly from the sixth to 

 the tenth day, is characterized by a display 

 of initial functional activity and/or reactiv- 

 ity by a variety of organs and tissues, to wit, 

 glycogen begins to accumulate in the liver 

 on the sixth day, gradually increasing on 

 subsequent days; blood sugar, although pres- 

 ent earlier, increases in concentration; and 



