66 ME. SWALE VINCENT ON THE 



There is no essential difference in structure between the more anterior and the more 

 posterior paired bodies. But, as Balfour has pointed out, the ganglionic development 

 is more abundant in the case of the anterior ones. The presence of nerve-cells in the 

 substance of the body itself is also more frequent in the case of the anterior suprarenals ; 

 in fact, nerve-cells are almost absent from the interior of the most posterior bodies, 

 which consist entirely of suprarenal tissue proper. 



The anterior pair or " axillary hearts," however, from their size and extensive 

 nervous connections, require a separate description. 



A longitudinal section of the " axillary heart " of Scyllium canicula, taken some, 

 where near its median part, shows that the body consists of an external and an internal 

 portion. The internal part is characterized by the above-described brown pigmented 

 cells 1. The external part on one side is composed to a great extent of large nerve-cells 

 with nerve-fibres running longitudinally. The nerve-cells are on an average 55 n in 

 diameter, but some of the oval ones may have a length of more than twice this number. 

 This formation extends for about two-thirds of the length of the gland. On the opposite 

 side and at the ends their external part is composed of the tissue which makes up the 

 bulk of the segmental bodies, viz. a very fine but irregular fibrous matrix enclosing 

 protoplasm with oval nuclei without definite cell-outlines ". 



At about a third of the length of the gland from the anterior end, a large group of 

 nerve-cells occupies the central part of the structure, and scattered nerve-cells are 

 distributed in other parts of the organ. 



In some instances {e. g. axillary hearts of Acanthias vulgaris) there are to be seen some 

 very large nuclei, twice or thrice the usual dimensions, and in addition one sees nuclei 

 of varying sizes down to the very smallest. 



This is not intended to be an exhaustive account of the histology of these bodies, 

 and with one more remark I will conclude for the present what I have to say about 

 them. I believe that many of the fibrils in the paired suprarenals (with the excejDtion, 

 perhaps, of the axillary hearts), which Balfour took for nerve-fibres, are in reality 

 nothing more than connective tissue, which, as we have seen, runs in an irregular 

 manner throughout the parenchyma. 



Interrenal Body. — I may as well state at the outset that I agree with the view that 

 this body corresponds with the cortical part of the suprarenal in Amphibians, Reptiles, 

 Birds, and Mammals. I am further of opinion that it is essentially a secreting-gland. 

 These conclusions have been forced upon me by its very close resemblance in structure 

 to the cortex of the suprarenal capsules of higher Vertebrates, and by its strikingly 



' The appearance of these pigment-cells is quite different from those which arc found in various organs and 

 tissues in iishes. There are in most cases no irregular masses or granules, but the whole cell, which has clear 

 and definite outlines, is of a uniform brown tint. In some few cases, however, the cells appear to be of the 

 ordinary coarsely granular type. 



^ Since the above was written, by careful examination of a good preparation with oblique light, I have 

 succeeded in making out the cell-jutliues in the " axillary hearts " of Sq/llium canicula. 



