Action of Calcium Upon the Pupil. 



87 



were some exceptions in which a larger dose had to be infused 

 before the pupil showed a distinct reaction to the calcium, and 

 then the contraction did not become maximal. These exceptions 

 seemed to occur when the rabbits were under profound ether 

 anesthesia. 



Atropin did not prevent this calcium myosis, but it retarded 

 somewhat the onset of this myosis and hastened its disappearance 

 after stoppage of the calcium infusion. Instillations of atropin into 

 the conjunctival sac were a little more effective than intravenous 

 injections. As far as we know calcium is the only substance which 

 is able to overcome the full mydriatic effect of atropin. 



What was said of atropin holds good, in general, also for 

 cocaine ; calcium overcomes the mydriatic effect of cocaine, but to 

 a less extent than that of atropin. The mydriatic effect of the 

 cocaine becomes especially active during the onset and the later 

 period of the calcium myosis. 



Ether.antagonizes moderately the calcium myosis. This is es- 

 pecially well seen when a few c.c. of ether are injected subcutan- 

 eously after a calcium infusion. The contracted pupils of the 

 rabbit now dilate fairly rapidly. As already mentioned, the cal- 

 cium myosis develops less readily when the animal is deeply under 

 ether. 



The action of adrenalin in animals whose superior cervical 

 sympathetic ganglion has been removed, is interesting. In these 

 rabbits, as is now well known, the instillation or subcutaneous, in- 

 tramuscular, or intravenous injection of adrenalin causes a strong, 

 long lasting dilatation of the pupil on that side where the gang- 

 lion was removed. Calcium overcomes this dilatation also, but 

 the mydriatic adrenalin-effect appears in a striking manner when 

 the calcium infusion is discontinued. While the pupil on the side 

 with intact ganglion remains strongly contracted, the pupil on the 

 operated side becomes very wide and remains so for hours. 



We have finally to mention that asphyxia also opposes moder- 

 ately the myosis brought on by calcium. 



We shall not enter here into a discussion of the intricate prob- 

 lem involved in the mechanism of calcium myosis ; our present 

 assumption is that this calcium myosis is produced by a stimula- 

 tion and contraction of the muscle fibers in the pupilary sphincter. 



