228 ANIMAL AUTOMATISM. [LECT. 



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 d 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 sen- 

 sory 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 d 

 priori, inasmuch as it depends on an organic 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 potentially 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 



