V ANIMAL AUTOMATISM 231 



quite contentedly, in the opposite direction, 

 towards the room of the concierge. The light of 

 the sun shining through a window now happened 

 to fall upon him, and seemed to suggest the foot- 

 lights of the stage on which he was accustomed to 

 make his appearance. He stopped, opened his 

 roll of imaginary music, put himself into the atti- 

 tude of a singer, and sang, with perfect execution, 

 three songs, one after the other. After which he 

 wiped his face with his handkerchief and drank, 

 without a grimace, a tumbler of strong vinegar 

 and water which was put into his hand. 



An experiment which may be performed upon 

 the frog deprived of the fore part of its brain, well 

 known as Goltz's " Quak-versuch," affords a 

 parallel to this performance. If the skin of a 

 certain part of the back of such a frog is gently 

 stroked with the finger, it immediately croaks. It 

 never croaks unless it is so stroked, and the croak 

 always follows the stroke, just as the sound of a 

 repeater follows the touching of the spring. In 

 the frog, this " song " is innate so to speak a 

 priori and depends upon a mechanism in the 

 brain governing the vocal apparatus, which is set 

 at work by the molecular change set up in the 

 sensory nerves of the skin of the back by the 

 contact of a foreign body. 



In man there is also a vocal mechanism, and 

 the cry of an infant is in the same sense innate 

 and a priori, inasmuch as it depends on an organic 



