30 Cincinnati Society of Natural History. 



minute, like reptiles their temperature is greater during incubation, 

 but is higher by 13^° F. than that of any other animal. 



Their temperature ranges from 45° F. to 112° F. ; this high 

 degree indicates a very great rtte of molecular change; their lungs 

 are not so large, nor are they so minutely divided as those of 

 mammals. Tiie respiratory system extends into the abdominal 

 and thoracic cavities, into the spaces between the muscles, beneath 

 the skin, and generally also into the larger bones, all affording a 

 great surface for the action of the air upon the blood, by this 

 means increasing the rate of oxygenation. 



It has been shown that birds will die immediately in an at- 

 mosphere in which a mouse will survive for a short time, and if we 

 go still lower in the scale we find that a frog will live for hours in 

 the same air. The cerebrum of the bird, which is not convoluted, 

 and the cerebellum are greater in size to that of any other verte 

 brate, as compared to the size of the body. 



This together with the folding of the cerebellum, gives them 

 greater locomotive power ; while the relative number of red cor- 

 puscles is not so great in birds as in mammals, it exceeds that of 

 reptiles and fish. 



The following table shows a great increase in the size of the 

 brain to that of the body in passing from the larger to the smaller 

 birds. 



Size of lirai/i to the I'ody. 



Goose 1 : 360 



Eagle \ : 260 



Cock 1:25 



Canary 1:14 



Humming iMrd i : 11 



Size of corpuscle in fractious of au. iucJi. 

 Ostricli -g i i, inches in diam. 



iVciVVll 9„, 



Swan ■ e'oB ' 



Pigeon rVer, 



IHick , , h'-o3 



Fowl 2 0*8 5 



Cock 2t'o-3 " 



Swallow 2 iS i) " 



Humming Bird 126*6 " 



Of the above, the ostrich has the greatest strengtli and phys- 

 ical endurance ; however the leading characteristic of birtl life (the 



