Muscles and Nerves 199 
When we carefully remove the upper part of a bird’s 
skull, we find that the brain occupies the whole interior, 
Fic. 145.—Comparison of skulls of Heron and Hawk, showing unlikeness caused 
by difference in manner of procuring food. 
the shell or box of bone which protects it being very thin, 
although strong. It would be very interesting if we could 
compare the short and thick bullet-shaped skull and brain 
