44 SECRETION 



degenerated so that it is assumed that a special receptive 

 substance exists at the myoneural junction. Smooth muscle 

 which has not been in connection with sympathetic nerve 

 fibers is unaffected. Thus, adrenalin causes a diminution of 

 tone of the small intestine and stomach and a disappearance 

 of peristalsis. Inhibition of the contractions of the urinary 

 bladder and gall-bladder; contractions of the uterus, vas 

 deferens, and seminal vesicles; dilatation of the pupil, stimula- 

 tion of the salivary and lacrymal apparatus are likewise caused. 



Adrenalin (C 9 H 13 NO 3 ) is to be found only in the medulla 

 of the suprarenal capsules. The cortex, as far as is known, 

 has a very different function. It is said to contain cholin, which 

 lowers blood pressure, and the attractive theory has been sug- 

 gested that in this way the suprarenal capsules exert a double 

 chemical control upon the circulation comparable to the double 

 nervous control. The existence of secretory nerves to the 

 suprarenal capsules has been made probable by the increase 

 of active substance in the suprarenal vein following stimula- 

 tion of the splanchnics. 



The amount of adrenalin necessary to produce a physio- 

 logical effect is extremely small. One-millionth of a gram per 

 kilo of body weight is sufficient to cause a distinct rise in blood 

 pressure. The action is but a temporary one, owing to a rapid 

 oxidation of the adrenalin. 



The active substance of the suprarenal capsules is furnished 

 by the so-called chromaffin cells which make up the medulla 

 and stain brown with chromic acid or chromates. An artificial 

 adrenalin has been synthetically prepared. Although chemi- 

 cally, like the natural substance, it is optically inactive, while 

 the other turns the plane of polarization to the left. The 

 synthetic product is said to consist of equal parts of levorota- 

 tory and dextrorotatory adrenalin. The artificial adrenalin has 

 only one-half the effect of the natural on blood pressure, so that 

 it is inferred that the dextrorotatory isomer has practically 

 no pressor effect. When these two isomers are separated the 

 left rotatory has the same pressor effect as natural adrenalin, 

 while the other, the right rotatory, has only ' one-twelfth to 

 one-fifteenth as much power. Adrenalin has the power of 

 producing glycosuria when injected. Repeated injections 

 lead to tolerance. 



