THE LIVING BIRD 17 



therefore be to examine briefly the vertebrate brain 

 and to see to what extent we are justified, on ana- 

 tomical grounds, in crediting a bird with inteUigence. 

 Just as the spinal cord is a centre for reflex ac- 

 tions, so is that part of the brain (originally the 

 anterior end of the spinal cord) known as the brain- 

 stem. It represents the oldest part of the brain in a 

 phylogenetic sense and in the lowest vertebrates 

 there exists but little else. In the more highly dif- 

 ferentiated of the lower vertebrate brains, say that 

 of a fish, various regions can be recognized in the 

 brain-stem, each of which is particularly concerned 

 with one of the senses of touch, taste, smell, sight or 

 hearing, respectively. In these centres, as in the 

 spinal cord proper, reflex arcs are organized and 

 completed. The response to an auditory stimulus 

 comes in the main from the auditory centre, a visual 

 stimulus elicits a response largely from the optic 

 centre and so on. They are not entirely independ- 

 ent, however, for they are connected by association 

 neurones but their connections are relatively scanty 

 fibre-tracts which do not lead to elaborate coor- 

 dination. Hence we find that fish, generally speak- 

 ing, are capable of only simple and rather stereo- 

 typed responses to external stimuli and they are, 

 naturally enough automatic, not intelligent, per- 

 formances. These connections can be improved by 



