106 INSTINCT 
The clasping of the female frog by the male during the 
breeding season affords a typical example of instinctive 
behavior; nevertheless, it occurs in entire independence of 
the higher nerve centers. ‘‘The Abbe Spallanzani showed 
that a male frog may have its head cut off during copulation 
without ceasing to cling tenaciously to the female. Goltz 
went still further and cut off the head of a male, then cut the 
body through between the third and fourth vertebra, and 
removed the viscera from the body cavity; the section of the 
frog that remained after these operations consisted of the 
first three vertebre, the pectoral girdle and the fore legs. 
Yet when the skin of the inner surfaces of the fore legs was 
rubbed with the finger this segment would show the same 
clasping efforts as a normal male frog.” 
Nearly all the characteristic responses of the frog will take 
place in individuals deprived of the cerebral hemispheres 
which are the part of the brain usually considered as the 
seat of intelligence and volition. Such a frog, if given suffi- 
cient time to recover from the shock of the operation, will 
leap about and swim spontaneously, snap at insects which 
come within range, bury itself in the mud on the approach 
of winter, and in many other ways behave in a normal 
ranine manner. 
Beginning with the anterior part of the brain and destroy- 
ing successively the parts of the central nervous system 
lying behind it, we cause, one after the other, the various 
instinctive acts of the frog to disappear, until we have left 
only the reflexes of the posterior part of the spinal cord. We 
reduce the frog to a more and more simple type of reflex 
mechanism, but we cannot say where the animal ceases to 
be more than a reflex mechanism of a complicated kind. 
The behavior of the frog is almost entirely made up of in- 
stinctive and reflex acts, many of which have their seat 
