222 ANIMAL AUTOMATISM. [LECT. 



its mouth is swallowed. On irritation, it jumps or 

 walks ; if thrown into the water it swims. If it be 

 put on the hand, it sits there, crouched, perfectly 

 quiet, and would sit there for ever. If the hand be 

 inclined very gently and slowly, so that the frog 

 would naturally tend to slip off, the creature's fore 

 paws are shifted on to the edge of the hand, until he can 

 just prevent himself from falling. If the turning of 

 the hand be slowly continued, he mounts up with great 

 care and deliberation, putting first one leg forward 

 and then another, until he balances himself with 

 perfect precision upon the edge ; and, if the turning of 

 the hand is continued, over he goes through the 

 needful set of muscular operations, until he comes to 

 be seated in security, upon the back of the hand. The 

 doing of all this requires a delicacy of co-ordination, 

 and a precision of adjustment of the muscular apparatus 

 of the body, which are only comparable to those of a 

 rope-dancer. To the ordinary influences of light, the 

 frog, deprived of its cerebral hemispheres, appears to 

 be blind. Nevertheless, if the animal be put upon a 

 table, with a book at some little distance between it 

 and the light, and the skin of the hinder part of its 

 body is then irritated, it will jump forward, avoiding 

 the book by passing to the right or left of it. 

 Therefore, although the frog appears to have no 

 sensation of light, visible objects act through its brain 

 upon the motor mechanism of its body. 1 



1 See the remarkable essay of Goltz, " Beitrage zur Lehre von den 

 Functionen der Nervencentren des Frosches," published in 1869. I 

 have repeated Goltz's experiments, and obtained the same results. 



