1885.] produced by the Application of Cocaine to the Eye. 433 



The mydriasis is quickly attained and very large, and differs also 

 from atropine in the pnpil acting always to light and accommoda- 

 tion. 



When the mydriasis is extreme, viz., 10 mm., the movement to light 

 is very slight, and the initial contraction can only be seen by magni- 

 fying the pupil by the observer's putting on a pair of -f 5D spectacles. 

 The slight contraction is immediately followed by a recoil which 

 almost induces the belief that a dilatation has taken place. 



The continuance of the mydriasis is comparatively short, the pupil 

 attaining its normal size in from twelve to twenty-four hours. By 

 drying the conjunctiva and cornea and placing the cocaine carefully 

 on a limited part, the dilatation of the pupil will at first only take 

 place at that spot, thus rendering the pupil irregularly dilated, and 

 showing the limited action of the drug. 



The following cases show the main points in- the mydriasis of 

 cocaine, and that the stronger the solution the quicker the initial and 

 ad maximum dilatation. 



I. H. C, 15. Pupils 6J mm. ; cocaine 4 per cent, on right eye at 

 2,5 p.m. ; at 2.25 p.m. pupil 10 mm., not further increased. The pupil 

 had resumed its normal size twelve hours afterwards. 



II. W. H., 30. Pupils 5 mm., cocaine 20 per cent, in left eye; in 

 seventeen minutes pupil 8 mm., and other instillations did not increase 

 its size. 



Pupil regained its normal size ten hours afterwards. 



III. E. W., 31. Pupils 5 mm., at 11.20 cocaine 2 per cent., at 

 11.30 cocaine 2 per cent., and at 11.50 pupils 8*5 mm. 



Fourteen hours afterwards pupil normal size. 



In rabbits the mydriasis induced by cocaine is, as a rule, very large, 

 and in two cases I could not make out any action to light, but in both 

 the pupil was 11*5 mm. ; and the reason probably was the great 

 stretching of the sphincter muscle of the pupil incapacitating its 

 action ; mydriasis was induced by conjunctival instillation, and also 

 by injection into the anterior chamber. 



Experiment II. — Cocaine and Atropine. 



In cases of full cocaine mydriasis the application of atropine had 

 no effect on the size of the pupil, but stopped its action to light and 

 accommodation. 



F. M., 25. Pupils 5*5 mm. ; two instillations of cocaine 2 per cent, 

 in right eye; pupil 9'5, acting to light and accommodation; atrop. 

 sulph. 5^ou grain, no increase in size of pupil, although atropine put 

 in three times, but the pupil did not act to light and accommodation. 



Experiment III. — Atropine and Cocaine. 

 On adding cocaine to an eye fully under the influence of atropine, 



