dered longer also, by the descent of the arched 

 midriff. What they gain in this way, however, 

 is less considerable, than what they lose by the 

 smaller scope of action in their ribs, than in 

 those in birds ; so that, after all, birds have, of 

 all vertebral animals, the most extensive respira- 

 tory, as well as the most energetic circulating 

 apparatus. 





