111. 
intfiligcitce of the ^ivh. 
^ THE ORGANS OF SENSE. 
We come now to the Intelligence of Birds ; 
but it would be difficult to define in what 
way it differs from that of the mammals, 
except, perhaps, in degree. It varies, of course, 
in different species ; it is greater in the rook 
than in the wren ; but it is always, so to 
speak, of the same kind or quality. Some 
naturalists, it is true, have denied them that 
faculty of understanding which the mammals 
possess ; will allow them nothing but that 
unconscious force or impulse which we call 
"instinct." But this theory cannot be main- 
tained in the face of careful observation and 
research. To admit the existence of such a 
, the brothers Miiller say, the last term of a false philosophy. 
4 
