THE ADRENAL BODIES 971 



The filtered extract was then injected intravenously, only a few drops 

 being required to evoke a marked rise in blood pressure. Some years 

 later AbeP succeeded in isolating this active agent by extracting the 

 gland with weak acid and benzoylating it, but the substance, which he 

 obtained was not the pure active principle but a benzoylated compound 

 of it. He designated this body as epinephrin. Later on Aldrich^ 

 and Takamine^ obtained its free base, and called it adrenalin. Since 

 then physiological chemists have determined its constitution as: 



HO 



H0< > - CH(OH) - CH2NHCH; 



It possesses an asymmetric carbon atom and, therefore, may be either 

 levo- or dextro-rotatory. Both these forms have been prepared syn- 

 thetically. Stolz and Dakin give its formula as C9H19NO3. 



Under normal conditions this agent is transferred from the medul- 

 lary substances into the suprarenal vein, whence it reaches the 

 general circulatory system by way of the inferior vena cava. The 

 active principle thus normally diverted into the blood-stream, is known 

 as adrenin. It need scarcely be mentioned that we may also em- 

 ploy the blood of the suprarenal vein in order to produce a rise in 

 blood pressure, but it should be remembered that adrenin is an unstable 

 body and decomposes very rapidly. This is the reason why the reac- 

 tion produced by it cannot be long continued. Even adrenalin is an 

 unstable and weak base, but is more stable as a dry, free base or as 

 the hydrochlorid, in which form it may be kept for some time unless 

 unduly exposed to the light and air. The amount of adrenin present 

 in the gland may be estimated by colorimetry as well as by the ampli- 

 tude of the circulatory reaction produced by it, i.e., by physiological 

 means.* Its free base is extremely potent; as little as 0.000002 

 gram sufficing to evoke a marked change in the blood pressure. The 

 suprarenals of human adults contain 1.0 per cent, of adrenin, those of 

 the cat 0.15 per cent., and those of rabbits, dogs, and monkeys from 

 0.2 to 0.3 per cent. In this connection, it is also of interest to note 

 that the parotid gland of the Jamaican toad secretes a similar principle 

 in amounts equaUing 5.0 per cent. 



The Action of Epinephrin upon the Circulation. — The most charac- 

 teristic action of extracts of the adrenal bodies or of the commercial 

 preparation adrenalin is a rise in blood pressure and a slowing of the 

 heart beat. But since these effects are usually obtained by injecting the 

 diluted adrenalin into the venous blood-stream, a certain time must 

 elapse before it can reach the arterial system to activate the vasocon- 



1 Bull. Johns Hopkins Univ., 1898. 



2 Am. Jour, of Physiol., v, 1901, 457. 



3 Jour, of Pharm., Ixxiii, 1901, 523. 



^ Folin, Cannon and Denis, Jour. Biol. Chem., xiii, 1912, 477; Seidell, ibid.^ 

 XV, 1913, 197, and Steward, Jour. Exp. Med., xiv, 1911, 377. 



