22 EVOLUTION AND DISEASE. 
in company with several others, are preserved in the 
museum of the Royal College of Surgeons (fig. II). 
The additional supply of blood to a part abnormally 
functional or irritated seems to be largely due to nervous 
influence, as the following experiments show. Bidder 
excised a piece of the sympathetic nerve in the neck of 
a young growing rabbit. This was followed by over- 
Fic. 11.--The head of a cock with its spur transferred 
to the comb. 
growth of the ear of the same side. The experiment 
has been repeated by Sterling on young and growing 
rabbits, and on dogs. A piece of the vagus and sym- 
pathetic—for in dogs both nerves are contained in the 
same sheath—was excised. In all cases the ear on this 
side became distinctly longer, broader, and somewhat 
thicker than its fellow. The hair was longer and 
