PHYSIOLOGICAL ACTION OF LIGHT. 149 
Rassir’s EyYE—(Continued). 





Observa- Before After After Effect of Effect of 
tions. impact. impact. removal. impact. removal. Remarks. 
61 200 196 No effect | Fall of 4 No rise } Eyereadjusted ; lightfrom 
62 195 193 No effect | Fall of 2 No rise magnesium lamp. 
63 240 236 237 Fall of 4 | Rise of 1 | Hg readiastede eeonete 
64 235 233 234 | Fall of 2 | Rise of 1 | { Dee 
65 244 242 243 Fall of 2 | Rise of 1 | { nee 2 
66 245 243 245 Fall of 2 | Rise of 2 | J : 
67 245 243 244 Fall of 2 | Rise of 1 Eye readjusted. 
68 248 247 248 Fall of 1 | Rise of 1 
69 244 240 244 Fall of 4 | Rise of 4 
70 242 239 240 Fall of 3 | Rise of 1 | Source of light from mag- 
71 240 238 238°5 Fall of 2 | Rise of 5 \ nesium flame, passed 
72 240 237 No effect | Fall of 3 No rise through 14 inch of 
73 236 234 No effect | Fall of 2 No rise | water. 
74 234 232 No effect | Fall of 2 Norise |) 





The result of the above twenty observations is that the impact of light 
produced a fall in the electro-motive force of about two degrees on the impact 
of light, while on the removal of light there was a rise of about one degree in 
most cases ; but in a few there was no rise at all. 
IJ].—ErFrects oF LIGHT ON THE EYE OF THE FROG REMOVED FROM THE HEAD 
IMMEDIATELY AFTER DEATH. 
At this stage of the inquiry it became evident that, owing to the rapid 
death of the nervous textures of warm blooded animals, it was difficult to 
obtain sufficiently great galvanometrical readings, the variations of which could 
be readily observed. We, therefore, began to employ the eye of the frog, the 
tissues of which, as is well known, retain vitality long after the systemic death 
of the animal. The eye was prepared by removing as far as possible all adhe- 
rent tissues from the sclerotic, and was so placed between the electrodes that 
one electrode touched the cornea, while the other was in contact with the trans- 
verse section of the optic nerve. When the eye was placed in this position a 
large deflection was obtained, and frequently it was so great as to pass beyond 
the scale. As was the case with the eye of the rabbit, the electro-motive force 
slowly fell to a point at which it was on the whole tolerably permanent. Read- 
ings were not made until it reached this stable condition. To secure not only a 
large deflection, but also sensitiveness to light, accurate adjustment of the eye- 
ball on the cushions was necessary. 
Ten series of experiments were made on ten frogs. 
At this stage of the inquiry, it was found necessary to adopt arrangements 
for securing a sudden impact and a sudden removal of light without being obliged 
on each occasion to extinguish the flame which was the source of the light. For 
VOL. XXVII. PART I. 2 Q 
