PHYSIOLOGICAL ACTION OF LIGHT. 153 
Experiments on the Eye of « Frog with a sudden Flash of Light. 
A non-luminous Bunsen flame was held at a distance of 24 feet, and it was 
rendered instantaneously luminous by quickly placing the finger and thumb 
over the two air-holes at the base. The following are the results — 
Observations. Before the flash. After the flash. Rise. 
118 51 53°5 213) 
119 53 55 2 
120 53°2 56 2°8 
P21 53 56 3 
122 53 55°5 eb) 
7B) 53 55 2 
The Bunsen flame was removed to a distance of eight feet, and the experi- 
_ment was repeated. 
Observations. Before the flash. After the flash. Rise. 
124 53°2 55 1°8 
125 53°2 54°8 1°6 
126 53°2 54°6 1°4 
127 53°2 54°4 1°2 
128 53°8 54°4 6 
129 53°9 55 etl 
A series of observations of a similar nature to those just detailed were made 
on one of the eyes of other five frogs with exactly similar results; and it appears 
to us it would serve no useful purpose to give these in detail. 
Experiments on the Action of Diffuse Daylight. 
A number of observations. were now made on the action of daylight on the 
eye of a frog. In these experiments diffuse daylight was admitted into the 
totally dark room by removing a piece of cardboard from one of the panes of 
the window. The following were the results :— 





Observa- Before On im- During Removal Effect of Effect of Temaniks 
tions. impact. pact. light. of light. impact. removal. i 
| 
130 85 100 100 105 Rise of 15 Rise of 5 
131 135 140 140 142 Rise of 5 Rise of  2* 
132 214 220 225 228 Rise of ._6 Rise of 3 |* Eye readjusted on 
133 230 240 240 250 Rise of i0 Rise of 10 pads. 
134 235 250 250 255 Rise of 15 Rise of 5 
125 274 285 285 290 Rise of 11 Rise of 5 | Gradual rise of the 
136 292 300 305 307 Rise of 8 Rise of 2 electro - motive 
137 310 326 326 328 Rise of 16 Rise of 2 force during this 
138 314 330 332 340 Rise of 16 Rise of 8 experiment. 
139 325 338 338 342 Rise of 13 Rise of 4 






These experiments show that diffuse daylight produces results similar to 
those obtained by the action of rays from artificial luminous sources. 
The action of light on the eye of the frog may be briefly stated as follows : 
When diffuse light is allowed to impinge on the eye of the frog, after it has 
VOL: XXVII. PART I. 
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