232 ANIMAL AUTOMATISM V 



relation between its sensory nerves and the 

 nervous mechanism which governs the vocal 

 apparatus. Learning to speak, and learning to 

 sing, are processes by which the vocal mechanism 

 is set to new tunes. A song which has been 

 learned has its molecular equivalent, which poten- 

 tially represents it in the brain, just as a musical 

 box, wound up, potentially represents an overture. 

 Touch the stop and the overture begins ; send a 

 molecular impulse along the proper afferent nerve 

 and the singer begins his song. 



Again, the manner in which the frog, though 

 apparently insensible to light, is yet, under some 

 circumstances, influenced by visual images, finds a 

 singular parallel in the case of the ex-sergeant. 



Sitting at a table, in one of his abnormal states, 

 he took up a pen, felt for paper and ink, and 

 began to write a letter to his general, in which 

 he recommended himself for a medal, on account 

 of his good conduct and courage. It occurred to 

 Dr. Mesnet to ascertain experimentally how far 

 vision was concerned in this act of writing. He 

 therefore interposed a screen between the man's 

 eyes and his hands ; under these circumstances he 

 went on writing for a short time, but the words 

 became illegible, and he finally stopped, without 

 manifesting any discontent. ( >a the withdrawal 

 of the screen he began to write again where he 

 had left off. The substitution of water for ink in 

 the inkstand had a similar result, He stopped, 



