THE INTERRENAL BODY. 475 



lobules or alveoli. These are filled with polygonal cells, which 

 form the true parenchyma of the body. These cells are in my 

 hardened specimens not conspicuous by the number of oil- 

 globules they contain, as might have been expected from Leydig's 

 description 1 . They are rather granular in appearance, and are 

 mainly peculiar from the somewhat large size of the nucleus. 

 The diameter of an average cell is about '015 Mm., and that of 

 the nucleus about - oi to '012. The nuclei are remarkably 

 granular. The septa of the body are provided with a fairly rich 

 capillary network. 



At the first glance there is some resemblance in structure 

 between the tissues of the suprarenal and interrenal bodies, but 

 on a closer inspection this resemblance resolves itself into both 

 bodies being divided up into lobules by connective-tissue septa. 

 There is in the interrenal body no distinction between cortical 

 and medullary layers as in the suprarenal. The cells of the 

 two bodies have very different characters, as is demonstrated by 

 a comparison of the relative diameters of the nuclei and the 

 cells. The cells of the suprarenal bodies are considerably larger 

 than those of the interrenal ('021 to '03 as compared to '015), yet 

 the nuclei of the larger cells of the former body do not equal in 

 size those of the smaller cells of the latter ('009 as compared to 

 01). 



My observations both on the coarser anatomy and on the 

 histology of the interrenal body in the adult point to its being 

 in no way connected with the suprarenal bodies, and are thus 

 in accordance with the earlier and not the later views of Leydig. 



The embryology of this body (under the title of suprarenal 

 body) was first described in my preliminary account of the 

 development of the Elasmobranch Fishes 2 . A short account of 

 its embryonic structure was given, and I stated that although I 

 had not fully proved the point, yet I believed it to be derived 

 from the wall of the alimentary canal. As will be shewn in the 

 sequel this belief was ill-founded, and the organ in question is 

 derived from the mesoblast. Allusion has also been made to it 



1 Perhaps the body I am describing is not identical with Leydig's posterior supra- 

 renal body. I do not, as mentioned above, feel satisfied that it is so from Leydig's 

 description. 



2 Quarterly Journal of Microscopic Science, October, 1874. [This edition No. V.] 



3 I2 



