302 THE EVOLUTION OF ANIMAL BEHAVIOUR 
best studied, affords in hereditary biological outline, a sketch 
which subsequent acquisition, under experience, serves only to 
elaborate by the filling in of details and of the more delicate 
shading in behaviour. But in the higher animals, in which a 
period of youth is a time for the acquisition of experience—for 
experimentation and practice,—it might seem that the inherited 
biological legacy was of less importance. The “spinal animal,” 
as Dr. Sherrington calls it,—that is, the animal in which the 
spinal centres are isolated from the cerebral centres—goes far 
to disprove any such view. In them the cerebral senses and 
the brain find elementary co-ordination of the bodily move- 
ments an achievement already provided and to hand in the 
spinal cord. But when different animals are compared—frog, 
bird, rabbit, dog, and monkey—the permanent effects of sever- 
ance of brain connection, the effects which remain when the 
temporary period of disturbing “shock” is over, are more 
marked in the higher than the lower types. And concerning 
this, Dr. Sherrington says,* ‘The deeper depression of reaction 
into which the higher animal, as contrasted with the lower, 
sinks when made spinal, appears to me significant of this, that 
in the higher types, more than in the lower, the great cerebral 
senses actuate the motor organs, and impel the motions of th: 
individual.” 
Whether in the animal in which all direct connection be- 
tween the anterior and posterior portions of the central nervous 
system has been severed there is a double consciousness—a 
cerebral consciousness and a spinal consciousness—we are not 
in a position accurately to determine. If the generally accepted 
opinion, that the higher brain-centres constitute the sensorium 
or seat of consciousness, be correct, we must suppose that a 
maimed consciousness, with many avenues of experience closed, 
is retained in the anterior moiety, while the posterior is rele- 
gated to a condition of mere sentience at best. In any case all 
relation between the two is prevented. The two—if two there 
be—are rendered quite independent through severance of the 
cord in the region of the neck. But there is a point of view 
* Op. cit., p. 29. 
