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HUMAN ANATOMY. 



exhibit the characteristics of sympathetic cells. Indeed, 



FIG. 1526. 



Capsule 



Zona 

 glomerulosa 



sorv to the svmnathetic nervous system. 



rK^sStrf^^^vSSss 



- 2 S5hsft ss ^r^: 



as cortex and medulla, possess a different origin and function 



According to the investigations ol 

 Aichel, 2 the suprarenal in the higher 

 mammals first appears in close rela- 

 tion to the Wolffian body, the anlage 

 arising from the proliferation of meso- 

 blastic cells at the ends of invaginations 

 of the mesothelium lining the body- 

 cavity. The individual cell-groups 

 thus arising with the several invagina- 

 tions fuse into the general anlage of the 

 sujirarenal. The primary close asso- 

 ciation of the latter with the Wolffian 

 body is later lost, the subsequent mi- 

 gration of the organ bringing it into 

 secondary relation with the permanent 

 kidney. 



Regarding the origin of the me- 

 dulla two views obtain. According 

 to the one generally accepted, the 

 medullary portions are developed from 

 cells which are derived from the ad- 

 jacent embryonic sympathetic gan- 

 glia, the chief support of this opinion 

 being found in the close correspond- 

 ence of the medullary cells with the 

 chromaffin elements of sympathetic ori- 

 gin occurring in other localities, such 

 cells wherever found exhibiting an 

 especial affinity for chromium salts. 

 When fully developed, the medullary 

 cells may be regarded as highly special- 

 i/ed cells which elaborate a powerful 

 stimulant that, when injected into the 

 blood, produces increased contraction 

 of the heart-muscle and of the invol- 

 untary muscle of the arteries. The 

 other view ;rttributes the origin of 

 the medullary cells to the same meso- 

 blastic anlage that produces the cortical 

 cords. The differentiation of the su- 

 prarenal into cortex and medulla occurs 



;'.",' in iiYi.-.".": comparatively late and long after the 



primitive organ has become sharply de- 

 fined from the Mil-rounding tissue. For a time the entire organ consists of cells \\hich 

 !. -ntii.il in appearano-. I hiring the third month this common tissue differenti- 

 \ .uxl medulla, in consequence of the breaking up of the outer zone into 

 :mar ma^es by the advent of connective-tissue trabecul.e from which delicate 

 tibrill.i- arise, forming the inner boundary of the cortex. Within the central part of 

 the oi-.m thu-H di-tmed minx-roil^ venous capillaries appear and break up the tissue 



1 X'iiu .-lit J<nirr..il <>f An.itomv anil Physiology, vol. xxxviii., 1903. 

 7 Anliix t. mikif. An.it., l'.l. Ivi., 1900. 



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Medulla 



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