50 



The Endocrine Organs 



apparatus; but negative results were obtained with rabbits and other 

 rodents. In epinephrectomised animals pigmentation of the skin is not 

 seen ; it therefore probably requires a gradual destruction, such as occurs 

 in chronic disease of the capsules in man, a condition which has not hitherto 

 been successfully imitated in animals. Some observers have described 

 obscure pigmentation of the skin and mucous membranes in animals as 

 the result of removal of the adrenals, or as the effect of removal of one and 

 injury of the other, but the evidence that the pigmentation was produced 

 Jby the operation is inconclusive. 



Morphology 



It is well known that the suprarenals consist of two parts, cwtex and 



medulla (fig. 32), which, 

 although anatomically 

 united in many animals, 

 are morphologically dis- 

 tinct and are developed 

 from different embryonic 

 formations ; the cortex be- 

 ing formed from meso- 

 derm-cells of the genital 

 ridge, whilst the medulla 

 is developed from cells 

 which belong to the same 

 neuroblast-masses as give 

 rise to the nerve-cells of 

 the sympathetic ganglia. 

 The cells of the medulla 

 are characterised by the 

 brown colour which they 

 strike with chromic acid 

 and its salts (chromaphil 

 reaction) (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 the 

 kidney on each side. In birds and reptiles and amphibia the renal and 

 adrenal tissues interlock. It is only in mammals that the same condition 

 is found as in man, viz., a central medulla with an enclosing cortex. 



Accessory suprarenals are not infrequent. They consist either of 

 cortical substance alone or of medullary substance alone, or of the two 

 combined. They occur most commonly between the kidneys and along the 

 lower part of the abdominal aorta as far as its bifurcation. In the male 

 rat 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 power, 

 c, cortex ; m., medulla. 



