24 



Scientific Proceedings (30). 



munication, however, it is not so much the time of initial dilation 

 as it is the time required for complete antagonism of the light 

 stimuli by adrenalin that is considered. The degree of resistance 

 to this antagonism is perhaps best illustrated by the appended 

 protocols, each taken from a series of experiments. Here it is 

 shown that maximal dilation and loss of light reflex in the guinea 

 pig results within 23 minutes after instilling 6 drops of i : 1000 

 solution of adrenalin chloride. After instilling 2 drops ev'^ery 2 

 minutes into the eyes of the following, maximal dilation and loss 

 of light reflex results : In the rabbit, within 56 minutes ; the dog, 

 96 ; the cat loi ; whereas in the monkey it requires 148 minutes ; 

 and in normal man even longer. 



From the protocols it will be seen that adrenalin not only di- 

 lates the pupil of the mammalian eye, but that in each case the 

 stimulating effect of light of moderate intensity can be completely 

 overcome by it. Furthermore the ease with which this antagonism 

 is accomplished seems to depend upon the degree of development 

 attained by the light reflex mechanism, since in animals that have 

 a sensitive light accommodating mechanism most highly developed 

 the period of instillation and amount of solution must be increased 

 to produce mydriasis, whereas in animals with a reflex mechanism 

 less sensitive to light stimuli, mydriasis is relatively easy. In con- 

 clusion it seems that these facts must be considered in formulating 

 a theory dealing with the dilator mechanism of the eye or with the 

 value of the adrenalin test for certain pathological conditions. 



I. Normal guinea pig. Sept. 5. Park, Davis & Co.'s I : 10000 adrenalin chloride. 



10.30 A. M. Before instillation, diameter of right and left pupil about 5 mm. 



10.32 " two drops instilled in right eye. 



10.36 " right pupil 5.8 mm., left pupil 5 mm. 



10.39 " " " 6 mm., left pupil 5 mm. 



10.43 " two drops instilled into right eye. 



10.45 " right pupil 7 mm., left pupil 5 mm. 



10.50 " " " 7.8 mm., left pupil 5 mm. 



10.51 " two drops instilled into right eye. 

 10.55 " right pupil 9 mm., left pupil 5 mm. 



1 1. 1 1 " " " 9 mm., practically dilated to a maximum. 

 12.32 P. M. " " aboutsameasatii.il. 



1. 15 " " " 7^ mm., left about 5 mm. 



1.24 " " " about same as left. 

 Maximum dilation brought on by six drops. Time required was about 23 min., 

 at the end of which time the pupil no longer reacted to light. 



