INTERNAL PROTECTIVE SECRETIONS 



45 



"suprarenal capsules" analogous to those described in mammals, but 

 possess two sets of perfectly distinct organs : 



(a) The inter -renal body, an unpaired glandular structure, 

 homologous with the cortical substance of the adrenal gland in 

 mammals. 



(&) The suprarenal bodies, arranged in pairs, in close relation 

 to the ganglia of the sympathetic chain, homologous with the 

 medullary or chrornath'ne substance of the adrenal glands. 



These results have been confirmed and amplified by recent 

 workers, among them being 

 Diamare and Giacomiui in 

 Italy. ' 



'The work of embryologists 

 (of Kohn, in particular) on 

 mammals, including man, has 

 fully confirmed the double nature 

 of the suprarenals. In fact, 

 while the cortical substance is 

 mesoblastic in origin (Wolffian 

 body), the medullary substance 

 is derived from the phaeo- 

 chronioblast, one of the two 

 groups of embryonic cells into 

 which the primary sympathetic 

 (ectoderrnic) cells become differ- 

 entiated. All such chrornamne 

 or chromaphile cells derived 

 from sympathetic ganglion rudi- 

 ments were classified by Kohn 

 as parayanglia. At a later 

 period of development the bulk 

 of the chromafhne or (as Poll 



termed it) pliaeOChrOme tissue Fl(; . io._ Scl i e , nat j c reconstruction of paragang- 



lion in new-born rabbit. (.A. Kohn.) A, aorta; 

 ' ', suprarenal body ; P, abdominal paragang- 

 lion, which, with "its prolongations, joins the 

 niedull.-iry substance of the suprarenal cap- 

 sides ; p,p, p, small nodular paraganglia. 



enters into relation with the 

 epithelial substance of the 

 cortex, in which it is englobed, 

 and thus forms the medulla of 

 the gland or "suprarenal paraganglion " (Fig. 12). The whole 

 of the chromaffme tissue derived from the mother-cells of the 

 sympathetic ganglia is not, however, enclosed in the capsule : 

 some of the smaller masses remain in various regions more 

 or less adherent to the sympathetic ganglia or the blood-vessels. 

 These nodules of chromaffine substance constitute the carotid 

 and sacral glands, Zuckerkandl's parasympathetic lody or abdo- 

 minal aortic, paraganglion, etc., which have long been observed 

 without definite knowledge as to their origin and significance 

 (Fig. 13). They are now shown by recent work in embryology, 



