The Comparative Physiology of the Suprarenal Capsules. 71. 



is clear from the fact that when the material (in spirit) is kept for 

 some time, this brown colour increases in intensity, although the 

 extract may become quite inactive. I have found extracts in 80 per 

 •cent, alcohol become quite inactive after a lapse of two months.* The 

 brown coloration appears to be the result of the oxidation of a 

 chromogen previously existing in the extract. 



It will have been observed that in the foregoing experiments the 

 extract of the interrenal body produced a certain effect upon blood- 

 pressure ; this I believe can be entirely explained as the result of 

 more or less admixture with " medullary glands." The latter are to 

 be found close by the side of the former, so that it is practically 

 impossible to remove it Without some of them adhering. In my 

 later experiments I tried to avoid this contamination by very careful 

 removal of the interrenal, and, although I have not succeeded by 

 this means in getting an extract of the interrenal quite inactive, yet 

 I find that the more carefully it is removed, the less effect is pro- 

 duced by an injection of its extract. Thus I found the rise of blood- 

 pressure due to interrenal to be much less when I had changed knife 

 and forceps after removal of the medullary bodies, so as to avoid con- 

 veyance of the active principle in this manner. 



Another explanation might be urged. The Polish physiologists 

 find that a slight rise of blood-pressure is produced by an extract 

 obtained from cortex only, and if this were the case it is conceivable 

 that my results, in the case of the interrenal, are due to this slight 

 specific action. But, when the greatest care is taken to avoid con- 

 tamination, Oliver and Schafer find the cortex quite inactive. 

 Besides, the " cortical " glands of Teleosts give no effect and there 

 can be little doubt that these are strictly homologous to the inter- 

 renal of Elasmobranchs. 



The morphological conclusion that the two kinds of gland in 

 Elasmobranch fishes really correspond to the cortex and medulla of 

 mammalian suprarenal is not without its physiological significance. 

 The cortex is always much more abundant than the medulla in 

 mammals, resembles a secreting gland in many points of structure, 

 and has possibly a function distinct from the medulla. The anatomi- 

 cal union of the two constituent portions may be in some sense 

 accidental. 



Conclusions. 



1. The suprarenal capsule of the mammalia corresponds to two 

 distinct glands in Elasmobranch fishes, the medulla corresponding 

 in structure and function to the " paired segmental " suprarenal 



■of potassium, and this constitutes a ready means of displaying them in a dissection 

 (Semper). This test probably applies to "medulla" throughout the vertebrata. 

 * When there is free access of air. 



