THE ENDdCBINE ORGANS, OR DUCTLESS OLA 7-17 



substance which reacts with epinephrine. This substance may be ; 

 duced either al the junction between the nerve and muscle the myo- 



aeural junction, or perhaps throug] i the protoplasm itself. It is 



failed the receptor substance of Langley, and is believed to read not 

 only with epinephrine, bul also with various drugs. The receptor bud- 

 stance seems to increase, it' no1 in amount, ;it leasl in sensitivity 

 the removal of t he nerve control. 



Ergotoxin, which is an amine obtained from ergol and also from <■■ 

 tain of the products of histidine, lias an action on the receptor substance 

 which is inhibitory and therefore antagonistic to thai of epinephrine. 



The antagonistic action of ergotoxin affects the excitatory bul not 

 the inhibitory actions of epinephrine. By using this drug we are en- 

 abled to show that, although the main effect of epinephrine on tissue is 

 excitatory, a less marked inhibitory influence may be simultaneously 

 developed. The inhibitory effed may also sometimes be evoked by 

 doses of epinephrine very much smaller than ihose used to produce 

 excitatory effects. These facts are well illustrated in the case of tho 

 muscle fiber of the blood vessels. With an ordinary dose of epinephrine 

 constriction occurs; after ergotoxin the same dose of epinephri ises 



dilatation. Or this latter result may also be obtained by administer- 

 ing to a normal animal quantities of epinephrine that are very much 



smaller than the usual quantity. The coexistent E inhibitory and 



citatory influence is also well noted in the case of the uterus. In some 

 animals the effect of epinephrine on this organ is to augment its rhythmic 

 contractions, in others lo inhibit them. In the former case, however, if 

 ergotoxin is first of all administered, epinephrine in its usual d< will 



invariably produce an inhibitory effect. The ergotoxin no doubt acts on 



the receptor substance, and similar effects have also been produced with 



apocodeine. 



Although ii is especially on plain muscular fiber having a sympathetic 

 nerve supply that epinephrine unfolds its action, yet, accordii Can- 



non, it increases the contracting power of voluntary muscle and dimin- 

 ishes the tendency to fatigue.* 



•For further details of th< s the pa 



