Influence of Ergotoxin on Pupil. 



7* 



drug causes a contraction of the pupil. His studies were made on 

 cats. 



I have found that in rabbits, ergotoxin produces exactly the 

 opposite effect. That is to say with all doses a dilatation of the 

 pupil lasting several hours results. With doses of I mg. per kilo, 

 which did not cause any marked general intoxication, the pupil 

 dilated to 7^ mm. from an original size of 5 mm. With doses 

 of 2 mg. per kilo, the pupil reached a size of 9 to 10 mm. All 

 injections were in the ear vein. 



These larger doses cause a certain amount of disturbance of 

 the respiration, and it might be claimed that the dilatation was 

 due to asphyxia. In fact Dale ascribes a dilatation mentioned by 

 Kobert in a protocol, to this cause. In order to exclude this 

 factor I curarized a number of rabbits and under artificial respira- 

 tion, injected ergotoxin. The heart was not markedly disturbed, 

 but the dilatation of the pupil was even greater than in most of 

 the normal animals. 



We may then assume that the dilatation seen in the rabbit's 

 pupil is not secondary to asphyxia but is due to the action of the 

 drug itself. 



Dale states that ergotoxin exerts two distinct actions on the 

 sympathetic nervous system. First a stimulation of the muscle 

 fibers of certain organs, notably the uterus. Second a paralysis 

 of the motor myoneural junctions of the true sympathetic. It is 

 to the latter action that the constriction of the cat's pupil is said 

 to be due. It is possible either that ergotoxin acts in a different 

 manner in the two species, or that the first action, direct stimu- 

 lation of the muscle fibers is exerted on the dilator muscle of the 

 rabbit's pupil and overcomes the effect of paralysis of the myo- 

 neural junction. The view that ergotoxin acts at least in part, 

 directly on the muscle fiber, is perhaps favored by the occurrence 

 of dilatation from ergotoxin, in two rabbits which were anesthe- 

 tized with ether until the light reflex was abolished. 



That the action of ergotoxin is not exerted on any more central 

 structure of the dilating mechanism is proved by the fact that its 

 action is little influenced by ganglionectomy. 



I recently reported that in rabbits, ergotoxin caused a very 

 marked rise of temperature. That the pupil dilatation is not 



