228 ANIMAL AUTOMATISM. 



in such a manner as to separate the hindermost division 

 of the brain from the rest of the organ, and suppose the 

 foremost two-thirds of the brain entirely taken away. 

 The frog is then absolutely devoid of any spontaneity ; 

 it sits upright in the attitude which a frog habitually 

 assumes ; and it will not stir unless it is touched ; but 

 it differs from the frog which I have just described in 

 this, that, if it be thrown into the water, it begins to 

 swim, and swims just as well as the perfect frog does. 

 But swimming requires the combination and successive 

 co-ordination of a great number of muscular actions. 

 And we are forced to conclude, that the impression 

 made upon the sensory nerves of the skin of the frog 

 by the contact with the water into which it is thrown, 

 causes the transmission to the central nervous apparatus 

 of an impulse, which sets going a certain machinery by 

 which all the muscles of swimming are brought into play 

 in due co-ordination. If the frog be stimulated by some 

 irritating body, it jumps or walks as well as the com- 

 plete frog can do. The simple sensory impression, act- 

 ing through the machinery of the cord, gives rise to 

 these complex combined movements. 



It is possible to go a step farther. Suppose that only 

 the anterior division of the brain so much of it as lies 

 in front of the " optic lobes " is removed. If that oper- 

 ation is performed quickly and skilfully, the frog may 

 be kept in a state of full bodily vigour for months, or 

 it may be for years; but it will sit unmoved. It sees 

 nothing; it hears nothing. It will starve sooner than 



