62 PHYSIOLOGY CHAP. 



question of the modifications suffered by the active suprarenal 

 principle when it is introduced into the body of the animal, as 

 also of its remote action when it is given many times in succession. 

 The following are some of the data : 



Langlois (1898) attempted to clear up the mechanism of the 

 destruction of the active principle of the capsule. According to 

 him it is rapidly destroyed in vitro by the action of oxidising 

 agents. When introduced into the arterial system, its action on 

 the blood pressure disappears in less than three minutes. The 

 pressure can be maintained at a constant height by successive 

 small injections of extract of the gland, at about three-minute 

 intervals. The disappearance of the effect coincides with the 

 return to normal pressure. 



The duration of the effective period is in ratio with the 

 activity of metabolism. In the normal tortoise, in winter, the 

 action on the heart persists for about 3 hours; in the warmed 

 tortoise it disappears after 20 minutes. In cooled mammals the 

 increased pressure persists for 20-30 minutes. 



The destruction of the active substance may occur in all the 

 tissues ; but the liver takes a preponderating part. In fact, the 

 fluid obtained by maceration of hepatic tissue attenuates the 

 activity of the suprarenal infusion more than the maceration 

 fluids of all other tissues. Infusion of a small quantity of the 

 extract into the mesenteric vein has no effect; while blood 

 pressure always rises if it is injected into a vein of the general 

 circulation. The blood from the hepatic veins of an animal that 

 has received an injection of the extract is less rich in active 

 substances than the blood of another region. Lastly, if the 

 hepatic circulation be cut out, the period of arterial hypertony 

 is prolonged. 



Still the problem of the extremely rapid destruction of 

 adrenaline in the body does not seem, according to the most 

 recent work, to be definitely solved in Langlois' sense. Neujean, 

 indeed, held the methods by which Langlois attacked this problem 

 to be inaccurate, and concluded, after more exact research, that it 

 was still doubtful whether adrenaline is destroyed in the body 

 by oxidation. 



Later on Patta (1905-7) showed that when adrenaline is injected 

 into the muscles or subcutaneous tissue, it does not produce rise 

 of blood pressure, as it would if injected into a vein, because its 

 absorption is considerably delayed by the vaso-constriction pro- 

 duced at the point of application ; it remains unmodified and 

 physiologically active for over two hours. 



