340 THE DUCTLESS GLANDS [OH. XXIII. 



muscles is to increase their tone, so that a tracing obtained from them 

 resembles that produced by a small dose of veratrine, namely, a pro- 

 longation of the period of relaxation. The effect on involuntary 

 muscle is equally marked ; there is an enormous rise of arterial blood - 

 pressure due chiefly to a contraction of the arterioles. This is produced 

 by the direct action of the extract on the muscular tissue of the 

 arterioles, not an indirect one through the vaso-motor centre.* The 

 active substance in the extract that produces the effect is known as 

 adrenaline; it is the reducing substance alluded to above which is 

 confined to the medulla of the capsules, and is absent in cases of 

 Addison's disease. 



The capsules, therefore, form something which is distributed to 

 the muscles and is essential for their normal tone ; when they are 

 removed or diseased the poisonous effects seen are the result of the 

 absence of this internal secretion. 



Adrenaline has received various names from the different chemists (Abel, v. 

 Fiirth, Takamine, etc.), who have isolated it. It is very powerful ; solutions of one 

 part in a million will produce physiological effects. Its composition is shown by the 

 following formula: 



OH 



A OH 



\/ 



CH.(OH).CH 2 .NH.CH 3 



and it is therefore a methyl-amino derivation of catechol (Pauly, Jowett). Recently 

 compounds closely allied to it have been made synthetically (Stolz, Friedmann, 

 Dakin). 



Whethe^ this discovery will lead to the same kind of results, as 

 in the case of the thyroid, must be left to the future to decide. 

 There is already some evidence to show that injection of supra-renal 

 extract is beneficial in cases of Addison's disease. The discovery of 

 adrenaline itself is, however, one of immense practical importance. 

 Its action on the small blood-vessels is so powerful that quite weak 

 solutions applied locally will arrest haemorrhage. 



There are some points of interest in the development and com- 

 parative physiology of the supra-renals. In mammals the medullary 

 portion is developed in connection with the sympathetic, and is at 

 first distinct and outside the cortical portion which is developed in 

 connection with the upper part of the Wolftian body ; it gradually 

 insinuates itself within the cortex (Mitsukiri). In Elasmobranch 

 fishes the supra-renals consist throughout life of separate portions ; 

 one, the inter-renal body, is median in position and single ; this corre- 

 sponds to the cortex of the mammalian supra-renal ; extracts of this 

 are inactive, and in the Teleostean fishes, where it is the sole repre- 



* Although muscular tissue is spoken of in the above description, Brodie's work 

 hows that it is the sympathetic nerve terminals which are really affect ec 3 . 



