WHALES 



Figure Sy. The main arteries of {a) a Bottlenose Dolphin and {b) a horse. Shaded areas 

 consist mainly of elastic tissue. 



between total size on the one hand and lung weight or pulse rate on the 

 other. Thus, we might expect a similar correlation to exist also in respect 

 of the size of their hearts. Now, if we look at Crile's very accurate tables, 

 we find that the ratio of heart to body weight in hippopotami and sea- 

 cows is o "3 per cent, in elephants, giraffes, rats, beavers and seals o -4 per 

 cent, in rabbits, cats, guinea-pigs, chimpanzees and cattle 0-5 per cent, 

 in mice and bisons 0-7 per cent, in horses 0-8 per cent, and in zebras and 

 bats I -I per cent. It would therefore appear that the size of the heart is 

 not as closely related to the size of the body as we might have expected. 

 Experts believe that the size of the heart is also connected with other 

 factors, such as the speed and power the animal develops, and while the 



