RETINAL REFLEXES OF NARCOTIZED ANIMALS. 23! 



tions to this general rule. Thus Calianassa, a burrowing shrimp, 

 gave positive reactions with " light " and none with " darkness." 

 It is interesting to note in passing that certain animals normally 

 living or moving in darkness appear to give such a reversed re- 

 action. The well-known responses of the earthworm and of M va 

 arcnaria may be quoted. But the subject can not be pressed fur- 

 ther without more experimental evidence. 



In a large number of cases the animal also responds to mechan- 

 ical stimulation such as tapping the table on which the containing 

 vessel rests at a period at which the retinal reflex becomes evident. 

 The type of response is somewhat similar to that evoked by illumi- 

 nation changes and is often not yielded by the conscious animal 

 subjected to the same slight stimulus. It nearly always ceases to 

 produce a response much earlier than the " darkness " stimulus. 



The results that we have recorded above have some interest from 

 the pharmacological viewpoint. The action of the drugs employed 

 is by no means similar in higher species (cf. Cushny 7 ). 



Camphor, in the frog, depresses the brain, and later the spinal 

 cord, the action being a descending paralysis. There is no excite- 

 ment, the reflexes gradually disappear, and the animal lies com- 

 pletely paralyzed. In mammals convulsions, due to stimulation of 

 the higher areas of the nervous axis, are usually produced, and 

 gradually pass into depression, stupor, collapse, and death from 

 cessation of respiration, the cerebral cortex, medulla, and cord 

 being in turn paralyzed. The terminations of the motor nerves 

 are paralyzed in the frog by large doses (which may account for 

 our failure to elicit the retinal reflex with camphor), but not in 

 mammals. Menthol produces a similar series of phenomena, but 

 there is less tendency to convulsions. 



Phenol, in the frog, first causes depression and loss of spon- 

 taneous movements, later augmented reflex excitability, and finally 

 tonic convulsions (due to increased irritability of the spinal cord). 

 Complete paralysis of the central nervous system supervenes. 

 Similar symptoms are produced in mammals, but there is often no 

 preliminary stage of depression. The peripheral nerves and mus- 

 cles are not affected in mammals and scarcely, if at all, in the frog. 

 Benzene is stated to be much less toxic than phenol, though when 



