. The endocrine organs; an introduction to the study of internal secretion . ofthe sympathetic cells of the medullaare characterised by thebrown colour which theystrike with chromic acidand its salts (chromaphilreaction) (figs. 32, 34)This reaction is due to the presence of adrenalin (see p. 58). In fishes these two parts remain separate, but in all higher verte-brates they are united into one organ, which is generally attached to thekidney on each side. In birds and reptiles and amphibia the renal andadrenal tissues interlock. It is only in mammals that the same conditionis found
. The endocrine organs; an introduction to the study of internal secretion . ofthe sympathetic cells of the medullaare characterised by thebrown colour which theystrike with chromic acidand its salts (chromaphilreaction) (figs. 32, 34)This reaction is due to the presence of adrenalin (see p. 58). In fishes these two parts remain separate, but in all higher verte-brates they are united into one organ, which is generally attached to thekidney on each side. In birds and reptiles and amphibia the renal andadrenal tissues interlock. It is only in mammals that the same conditionis found as in man, viz., a central medulla with an enclosing cortex. Accessory suprarenals are not infrequent. They consist either ofcortical substance alone or of medullary substance alone, or of the twocombined. They occur most commonly between the kidneys and along thelower part of the abdominal aorta as far as its bifurcation. In the malerat such an accessory gland is almost constantly seen close to the epidi-dymis. They are relatively longer and more frequent in the new-born. FIG. 32.—Section of suprarenal, low , cortex; »«., medulla. Structure of Suprarenal Capsules 51 animal than in the adult, in which they may be missed altogether. Thepossibility of their presence must, however, be borne in mind when con-sidering the results of the extirpation of the adrenals in animals. Those accessory glands which have a structure and derivation similarto the medulla of the suprarenal capsules also contain cells which arecoloured brown by chromic acid. Such bodies have been termed para-ganglia by Kohn, chromaphil bodies by Vincent, chromajj/ine bodies bymost other authors. The carotid gland is of this nature. The coccygeal gland is contains no chromaphil cells and appears to represent an arteriovenousanastomosis which is met with in certain lower mammals. Paraganglia in-variably occur in close morphological and developmental connexion withsympathetic nerves and gangli
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