THE SUPRARENAL SYSTEM 



233 



latory (motor), as in the arteries of rabbits, in the heart, the 

 ileocascal sphincter, the urethra, the dilator muscle of the iris, 

 the pilomotor muscles and the retractor muscle of the penis, the 

 stimulatory action of adrenalin upon the sympathetic system is 

 more or less weakened by ergot poisoning, or may in some cases 

 even be abolished. 



Organ 



Effects of sympathetic stimulation and 

 of intravenous adrenalin injection 



Uterus (virgin, of the cat) 

 Uterus (pregnant, of the cat) 



,, (rabbit, ape) 

 Retractor of penis (dog) ... 



weak S. after electric 

 sympathetic stimulation. 

 I. or S. and I. ... I. 



S. ... I. 



S. ... I. 



S. N. 



S = stimulation; I = inhibition ; N = negative result. 



(3) Where the sympathetic in nervation is twofold, both 

 stimulatory and inhibitory in character, the stimulatory action 

 preponderating under normal conditions, as in the vessels of 

 the carnivone, in the spleen, the internal anal sphincter, the 

 urinary bladder of ferrets, the uterus of rabbits and apes, and 

 the pregnant uterus of cats, the action of adrenalin and the effect 

 of electric stimulation of the sympathetic are exclusively inhibitory 

 after ergot poisoning. It is evident from this that structures 

 having a sympathetic innervation do not all respond to the action 

 of ergot in the same manner. Those with inhibitory sympathetic 

 innervation are entirely uninfluenced; those with stimulatory in- 

 nervation become paralysed ; where both stimulatory and inhibitory 

 fibres are present, the inhibitory function, which was previously 

 masked by the activity of the stimulatory fibres, becomes apparent 

 as soon as these are put out of action. 



Dale's experiments show that the same structural elements 

 are influenced by the active principle of ergot as by adrenalin, 

 and that the site of this influence lies in the sympathetic myoneural 

 junction tissue. The inhibitory action of ergot is, however, con- 

 fined to the motor myoneural junction tissue. Whether or no 

 in organs with a double sympathetic innervation, the stimulatory 

 and inhibitory functions are associated with the same substratum 



