Ontogeny of Endocrine Correlation 



as a rule very early in embryonic life. Both 

 the chromaffin reaction of Henle and the 

 intestinal strip method agree in showing that 

 adrenaline is first detectable at a time when 

 small groups of future medullary cells begin 



591 



islands of cells proceeds progressively 

 through the cortex toward their definitive 

 topographical position, the quantity of adren- 

 aline gradually increases. In some species 

 the relative quantity present in late fetal 



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Fig. 210. Portion of adrenal coi'tex with interlacing cords free of intervening medullary tissue. Developed 

 in a chorio-allantoic graft from a small isolate just back of the primitive pit of a chick blastoderm of the 

 early head-process stage. Initial X 450. 



to enter the cortex from the contiguous sym- 

 patho-chromaffin primordium (cf. Figs. 209S, 

 210, and 211). As the migration of these 



mammals (cat, guinea pig, and rabbit) the adrenal 

 glands contain a high proportion of noradrenaline 

 and a small quantity of adrenaline, and, further, 

 the relative amounts of these two substances change 

 with advancing developmental age. The observa- 

 tion that the large amounts of noradrenaline present 

 in the adrenals of fetal and young postnatal mam- 

 mals generally diminish as the adrenaline con- 

 tent increases in still older animals led to the 

 suggestion that the amine noradrenaline is not 

 only a precursor of adrenaline but indeed may be 

 the hoi-mone of the adrenal gland "in the early days 

 of life." 



life inay be distinctly greater than in the 

 adult adrenal (McCord, '15; Fenger, '12). 

 This is in keeping with the observation that 

 in many species of mammals the relative 

 volume of the medulla to the whole adrenal 

 is high at birth, rapidly decreasing shortly 

 thereafter until puberty, when a stationary 

 condition is reached (Donaldson, '19). 



What is the significance of such an early 

 appearance and quantitative increase in 

 adrenaline? Could they possibly reflect the 

 "needs" of the growing embryo for adren- 

 aline in the operation of mechanisms, es- 

 pecially of those dependent on or controlled 

 by hormonal substances? Paralleling this 



