RETINAL REFLEXES OF NARCOTIZED ANIMALS. 219 



toxic effects appear as twitches of the limbs and claws, convulsive 

 strokes of the tail, while, when a number of animals are placed in 

 the same vessel, they cling to each other in an entangled mass 

 which is not easily separable. The convulsions are of such a 

 nature that the animal clings fast to the nearest object, especially 

 to the soft legs of its neighbors. If at this stage of camphor 

 poisoning before permanent paralysis sets in the animal is removed 

 rapidly to sea- water, the toxic effects just described muscular 

 twitchings and convulsions disappear rapidly. There remains, 

 Jiowcvcr, a pronounced photic over-excitability, which is mani- 

 fested by the animal making very pronounced springs when the 

 light intensity is rapidly increased, but on removal of the strong 

 light, violent springs and tail-strokes. . . . The rise of rcfle.v- 

 excitability on sudden lessening of light-intensity icas constant at 

 the same phase of cam'pJwr action. . . . There was no trace of a 

 reflex increase for tactile stimuli, neither by shaking the vessel, 

 nor by gently touching the head or tail." 



Similar results were obtained with phenol in sea-water. A con- 

 centration of i : 2000 was rapidly fatal, one of i : 5000 less rapid 

 in action. Removal to sea-water before complete paralysis per- 

 mitted the same light reactions to be observed, especially that of 

 removal of light. Strychnine, ammonia, and caffeine did not pro- 

 duce the effect. 



Frohlich and Kreidl point out that under natural conditions 

 various animals react more strongly to shadow than to sudden 

 increase of light intensity. Sarasin in 1887 (Diadcma sctosumY 

 and Uexkiill in 1896 (Centrospinus longispinns) 4 noted that sea- 

 urchins react to shadow but not to light with movements of the 

 spines, and Hess, in 191 5, r> showed that shadow, but not light 

 increase, produces in them rotating movements of certain flask- 

 shaped structures. Franz (i9i9) G has shown the existence of the 

 shadow reactions in snails. Frohlich and Kreidl consider that the 

 reaction is protective, and that the difference in the " cerebrally " 

 poisoned and centrally irritable Palcrmon is only quantitative. 



In the experiments now to be described we have endeavored to 

 link up the experiments of these workers with those of Cameron 

 and Sedziak, since the phenomenon is obviously the same in the 

 two series. 



