438 



Mr. W. H. Jessop. On the Mydriasis [June 18, 



the exposed sympathetic generally gave rise to an increase in the 

 dilatation of the pupil. 



On, however, carefully considering this, I found that it simply 

 depended on the size of the mydriasis, as in cases where the ad 

 maximum cocaine mydriasis was produced, stimulation of the sym- 

 pathetic no longer increased it, though the strength of the current 

 was increased. In some cases I found that the increase in the size of 

 the pupil on stimulating the sympathetic was due to the fact that the 

 animal was in a bright light, and therefore the pupil contracting to 

 that light. On shading the eyes, and the pupil assuming its full dila- 

 tation, no extra effect was produced by stimulating the sympathetic. 



I. Brown and White Rabbit. — Pupils 5 mm. X 6 mm, under chloro- 

 form, after five instillations of cocaine 2 per cent., left pupil 10 mm. 

 On exposing the left cervical sympathetic, and stimulating it by 

 faradaic current, no increase in mydriasis. 



TI. Brown Rabbit. — Pupils 7"5 mm. x 6 mm. ; left eye, four instilla- 

 tions of cocaine 4 per cent., pupil 10 mm. On stimulating cut end 

 by faradaic current, pupil 10 - 5 mm., being a very slight increase. 



This, however, was done in a bright light, and on shading the eye, 

 pupil 10 5 mm., and no increase no stimulating the cervical sym- 

 pathetic. 



Experiment XVII. 



In three rabbits the cervical sympathetic was exposed, a piece taken 

 out of it, and the wound stitched up, all the animals recovering 

 without a bad symptom. The pupils on the operated side were con- 

 tracted, but acted well to bright light. 



In all, after a time, the result was the same, namely, no effect on 

 adding cocaine, though applications often repeated, and of different 

 strengths. 



Large Brown Rabbit. — Pupils, under chloroform 9 mm. X 7 mm., 

 act well. 



Right eye, after 6 instillations of cocaine, 2 percent., pupil 12 mm., 

 and apparently they did not act to light. 



On left side the cervical sympathetic exposed and 15 mm. of the 

 nerve taken out, the upper end stimulated by faradaic current, and 

 pupil became 12 mm. 



The section was followed by contraction of the pupil to 7*5 mm. X 

 6*5 mm., and the other signs of cutting the cervical sympathetic. The 

 wound was carefully stitched up and the animal soon recovered. 



100 Hours Later. — Left eye, pupil oval, 6*5 mm. x 4*5 mm., but 

 contracts well to light. 



10.30, cocaine 2 per cent, on left eye. 



This was repeated five times without effect, the pupil remaining the 



same. 



