The Comparative Histology of the Suprarenal Capsules. 291 



and the sympathetic nervous system have been sufficiently emphasised. 

 Leydig [70 and 7I\ and Semper [106] have laid great stress on this 

 aspect of the question. It remains to say a word about their relations 

 to the blood- vascular systems. We have seen that each body is 

 placed on an intercostal artery which is a direct branch of the 

 aorta. This artery pierces the centre of the body and is always seen 

 in the middle of the section. But much more striking is the fact that 

 several of the anterior bodies (the number differs in different species) 

 are placed in the venous sinus, and during life are bathed in its blood. 



Interrenal Body. The interrenal body is an "ochre-yellow" rod- 

 shaped structure, paired in the Rays, unpaired in the Sharks, lying 

 usually in the region of the posterior part of the kidney, but sometimes 

 extending as far forward as its anterior extremity. It bears a striking 

 resemblance in its colour, general appearance, and relations to the 

 kidney to the suprarenals of the Anura, and in the first two of these 

 features, to those of the Reptilia. 



This organ is the primitive type of the suprarenal cortex and 

 corresponds in structure with the cortical part of the suprarenal body 

 in Amphibians, Reptiles, Birds, and Mammals. It will be seen that it is 

 very similar in structure to a secreting gland, as shewn by its definite 

 arrangement into alveoli and its markedly granular protoplasm (see 

 PI. XVI. fig. 4). 



The alveoli are arranged in many places in a radiating manner 

 round large veins or venous sinuses. In many of my sections ai-e 

 seen structures very like "demilunes" in Mammalian mucous glands 

 (PI. XVI. fig. 4 dc). The appearance of the interrenal body when 

 examined microscopically is so hke that of the "corpuscles of Stannius" 

 — the known suprarenal bodies of Teleostean fishes — that there 

 can scarcely be a doubt of the homology . between them (cf. PI. XVI. 

 figs. 4 and 7). This homology has been worked out in a separate 

 memoir by Diamare [25 and 26], 



The organ is made up of masses of cells, apparently solid, which we 

 may designate the glandular alveoli (PI. XVI. fig. 4). These vary in size 

 and shape in different groups of Elasmobranchs and even in different 

 species. Thus in the Rays they have a moi-e rounded form than in 



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