298 S. Vincent, 



darkening of the specks of suprarenal can be observed by the naked 

 eye^). It was found impossible also to get the tests for the chromogen 

 by making an extract. The extract, further, did not raise the blood- 

 pressure when injected into the blood-vessels of a living mammal^). 

 For these reasons extreme care has been employed in the liistological 

 examination. 



There can be no doubt that my former description of the two 

 kinds of tissue was in the main correct. I found, on looking up my 

 old slides that I had apparently relied entirely upon the characteristic 

 staining of the medullary cells with haematoxylin (vide infra pag. 302 

 and 306), having no specimens which had been hardened in bichromate. 

 This being rather unsatisfactory I have since employed Miiller's fluid 

 to detect with certainty the relations of the two substances. Tliese 

 two constituents, the cortical and the medullary, are as distinct as in 

 Anura, Eeptilia, Aves, and Mammalia, but the medulla is not present 

 in such large proportion as in any of these '^). 



The cortical substance presents the same histological features as 

 in the frogs and toads (q. v. infra), being composed of delicate solid 

 columns of cells interlacing in all directions. The structure of this 

 portion needs no further description. 



The medullary portion is represented by small masses of brown*) 

 cells, or even single cells, sometimes actually situated in the ganglia 

 of the sympathetic , sometimes further away from the ganglia and in 

 closer contact with the cortical cell-columns. The anatomical condition 

 is in fact an intermediate one between that found in Elasmobranchs, 

 where the two constituents are quite independent of one another, and 

 that found in the Anura and Eeptilia, where cortex and medulla have 

 come into close contact, but have only just commenced to be mixed 

 up together *"). In the ganglia or close to them one can sometimes 



^) This is in marked contrast to the behaviour of the suprarenals of the frog. 



^) This result can only be attributed to the insufficient amount of material 

 which one could obtain. 



^) Except perhaps in Hyla arborea, where I find the amount of medullary 

 substance to be very small. 



*) i. e. after bichromate treatment. 



^) This intermingling is complete in Aves (q. v. infra). 



