The Comparative Physiology of the Suprarenal Capsules. 65 



experimental evidence in favour of this view which I now wish to 

 put forward. Before doing so, however, it will be well to state here 

 that, so far as I have been able to make out, one only (viz., that 

 which corresponds to the cortex) of the two suprarenal constituents 

 is present in Teleostean fishes. The same probably applies to 

 Ganoids. 



With regard to the development of the suprarenals it is only 

 necessary to note that many observers believe that the medullary 

 portion is derived from, or at any rate, developed in connection with, 

 the sympathetic nervous system (Balfour, 1), and it seems clear from 

 the researches of Mihalkovics (8) that the cortex is developed from 

 the germinal epithelium. 



The researches of Oliver and Schafer (9, 10, 11), followed by 

 those of Cybulski and Szymonowicz (2, 3, 4, 13, 14), have shown 

 that the medulla of the suprarenal capsules of mammals and the 

 suprarenal capsules of birds and amphibians (Szymonowicz, 14) 

 (presumably the medulla only also in these), produce a remarkable 

 and characteristic rise of blood-pressure, when an extract is injected 

 into the circulation of a living animal. But, so far as I know, no one 

 has previously tested the effects of extracts of the suprarenal bodies 

 of fishes. 



The following experiments were accordingly undertaken at the 

 suggestion of Professor Schafer, to whom I am indebted for advice 

 and assistance on many points connected with the research. I have 

 already published a preliminary notice (17), giving the results of 

 initial perfusion experiments. I have now repeated and confirmed 

 these perfusion experiments, and, in addition, have tested the effect 

 of the materials in question upon the arterial system of mammals. 



Effects of Extract of Fishes 1 Suprarenals upon the Arterial System. — 

 The methods employed have been : — 



1. The perfusion of normal saline solution or Ringer's circulating 

 fluid containing the extract to be tested, through the blood vessels of 

 large toads after the brain and spinal cord had been destroyed by 

 pithing. 



2. The injection of the extracts into the blood-vessels of a living 

 mammal and recording in the usual way the blood-pressure tracing 

 with the mercurial kymograph. Dogs and cats have been used in 

 these experiments. 



The suprarenals employed in this research have been obtained 

 mainly from Scyllium canicula among the Elasmobranchs and from 

 Anguilla anguilla as a representative of the Teleosts, but I have also 

 used Scyllium catulus, Acanthias vulgaris, Galeus canis, and others in 

 the first-named order, and Gaelics morrhua and several other species 

 of Teleosts. The effects produced upon blood-pressure were practi- 

 cally identical in the corresponding organs of different species. 



