INTERNAL SECRETIONS 



509 



It hasTbeen shown that extirpation of the suprarenal glands almost 

 invariably causes death. The fatal result was at one time attributed 

 to an accumulation of toxic bodies within the organism. Such toxic 



FIG. 243. {SHOWING RISE OF BLOOD-PRESSURE DUE TO RELEASE OF PRESSURE ox 

 SUPRARENAL VEIN. (From " Internal Secretions," Swale Vincent.) (Gardner 

 and Gunn.) 



The vein has been compressed for some time and was released at point signalled. 



bodies were believed to be destroyed by the glands. It is now known 

 that the chief function of the suprarenal medulla is to furnish as 

 an internal secretion an active principle adrenalin. Adrenalin, as 

 its structural formula shows 



OH 



i 



OH 

 CHOH.CH 2 NHCH 3 



is an aromatic body nearly allied to tyrosin, and is probably derived 

 from tyrosin. 



The best-known function of adrenalin is its power to induce con- 

 striction of the smooth muscle of the arterioles, and thereby cause a 

 rise of arterial pressure (Fig. 238, A, B). The supply of adrenalin to 

 the blood is under the control of the splanchnic nerves. If these be 

 stimulated the arterial pressure is raised, but not after extirpation of 

 the suprarenals (Fig. 245). 



This is only one of the functions of adrenalin, for an intravenous 

 injection of adrenalin acts upon all smooth muscle supplied by the 



