Tke Comparative Histology of the Suprarenal Capsules. 301 



the organ ^). If the tissue has been hardened in alcohol, the cells 

 stain very deeply with haematoxylin, and the nucleus is not easily 

 seen. The cells are more irregular and somewhat larger, and the 

 nuclei have rather greater dimensions, than in the cortical cell-columns. 

 The nuclei are often oval. But the most striking feature about these 

 cells is that if the tissue has been hardened in Miiller's fluid (or any 

 other fluid containing bichromate of Potassium), they become stained 

 brown just as do the chromogenic cells in the paired suprarenal bodies 

 of Elasmobranch fishes. So that this structure is the "medulla". 



The medulla is small in amount in proportion to the cortex. The 

 organ has a very rich blood-supply (see PI. XVII. fig. 11 and PI. XVI. 

 fig. 12). A network of capillaries runs between the alveoli (PL XVI. 

 fig. 12), and large veins are abundant. 



There seems to be considerable difference between the various 

 species of the Anura in regard to the amount of medulla in proportion 

 to the cortex. This proportion is always small, but is particularly 

 so in Hyla arborea. 



The physiological identity of the suprarenal capsules of the fiog 

 with those of mammals has been placed beyond a doubt by the 

 researches of several authors. Thus Szymonowicz [1^2] has employed 

 extracts from a frog's siiprarenals in his experiments upon the alterations 

 of blood-pressure produced by such extracts. Langlois [69] has devoted 

 a separate paper to the subject. In conjunction with B. Moore [81], 

 I have chemically tested an extract made from the suprarenal capsules 

 of several frogs, and found that this gave the chromogen reactions in 

 a perfectly definite manner. These physiological and chemical reactions 

 of course only apply to the medullary substance. The evidence as to 

 the homology of the cortical substance is morphological and histological. 



VII. Reptilla. 

 While in Pisces and Amphibia the suprarenal bodies are in close 

 anatomical connection with the kidney, in the Reptilia they are inti- 

 mately associated with the reproductive apparatus. In the Lacertilia 



^) Forming a sort of irregular boundai'y between tlie substance of the kidney 

 and that of the suprarenal body. 



