IX.] ANIMAL AUTOMATISM. 221 



made 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 con- 

 tact 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 complete frog can do. The simple sensory 

 impression, acting 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 operation 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 un- 

 moved. It sees nothing; it hears nothing. It will 

 starve sooner than feed itself, although food put into 



