Ontogeny of Endocrine Correlation 



587 



tions in sex development, this has not been 

 substantiated for the mouse (Howard-Miller, 

 '27, '39; Howard, '46). According to Gersh 

 and Grollman ('39a,b), the function of the 

 x-zone and the more peripheral fascicular and 

 glomerular zones is identical; both respond 

 to stimulation but not equally, the x-zone 

 being less responsive. Furthermore, the wide- 

 meshed capillary plexus of the x-zone is 

 altered by excessive activity so as to resemble 

 more closely the capillaries of the fasciculate 

 zone (Gersh and Grollman, '41). (For a thor- 

 ough analysis of the relation of the adrenal 

 cortex to the reproductive system in fetal and 

 young postnatal rats, see Moore, '53.) 



The changes in vascular pattern of the 

 growing cortex offer a possible index of the 

 onset of functional activity (see Figs. 209^, 

 B, and C) . During the early stages of adrenal 

 growth in the embryo the arrangement of 

 the cortical cells is haphazard, at which 

 time the capillaries of the cortex are in the 

 form of a loosely woven and irregular plexus. 

 Vt later stages with the growth of the cortex, 

 portion of the cortical cells becomes ar- 

 ranged into parallel cords or columns of 

 the fascicular zone, the commonly supposed 

 secretory zone of the adrenal of juvenile and 

 adidt mammals. With this change in cellular 

 arrangement the earlier unoriented type of 

 capillary circvdation is gradually recon- 

 structed into a more or less longitudinally 

 oriented pattern of vessels, i.e., in rather sim- 

 ple lines the plan of the adult circulation 

 (Flint, '00; Whitehead, '33). The significance 

 of the changes in vascular pattern may be 

 interpreted in terms of function (Gersh and 

 Grollman, '41). The change is from a type 

 which permits a slow rate of blood flow to 

 one which favors a much more efficient flow 

 of blood, thus assuring a richer supply of 

 blood to the cortex. The fact that the more 

 efficient mode of blood transportation arises 

 as the cortical cells assume an organization 

 with distinctive properties seems to imply 

 a beginning functional relation and one 

 which, furthermore, may reflect the need of 

 the growing organism for the cortical hor- 

 mone in its metabolism. At least, such a 

 view is in keeping with findings on postnatal 

 mammals that in response to increased needs 

 of the organism for cortical hormone the 

 cortex hypertrophies and the vascular pattern 

 of a hyperactive cortex is altered so as to 

 increase blood flow. 



The question next arises as to when in 

 the com-se of adrenal development the ori- 

 ented type of circulation arises. According 

 to Flint ('00) the beginning of an orderly 



Fig. 209. Three stages in development of the vas- 

 cular pattern of the adrenal of the pig embryo 

 (adapted from Flint, '00). 



A, Stage of 3 cm. showing the simple irregular 

 plexus of capillaries of the cortex, which at this 

 stage is comprised of irregular cords of cortical cells. 

 Arrow indicates direction of blood flow from the 

 fibrous capsule (uppermost surface of figure) to the 

 central venule {v). Precursor medullary cells ap- 

 parently lie between cortex and capsule. 



B, Stage of 8 cm. showing the capillary plexus of 

 two groups of medullary cells (note resemblance to 

 glomeruli), which have invaded the cortex. Each is 

 separately vascularized by an arterial capillary 

 from the capsule. Capillary plexus of cortex is still 

 irregular. 



C, Stage of 22 cm. (near birth) showing the ori- 

 ented pattern of the capillary plexus of the cortex, 

 thus reflecting the initial zonation of the cortical tis- 

 sue. The definitive topographical relation of cortex 

 {cort.) and medulla {med.) is initially established 

 at about the 12 cm. stage, when the invading groups 

 of medullary cells reach their terminal position 

 adjacent to the central vein (jy). 



