BIRDS. 



Respiration Different abodes. 



body, and adhering to the under surface of the 

 bones. These, by their motion, force the air 

 through the true lungs, which are very small,, 

 seated in the uppermost part of the chest, and 

 closely braced down to the back and ribs. Mr. 

 John Hunter attempted by a variety of experi- 

 ments to discover the use of this general diffu- 

 sion of air through the bodies of birds ; and from 

 these he found, that it prevents their respiration 

 from being stopped or interrupted by the rapi- 

 dity of their motion through the air as a resist- 

 ing medium. 



The abode of the volatile tribes is very various ; 

 as they are found in every part of the known 

 world, from the hottest to the coldest regions. 

 Some species are confined to particular coun- 

 tries; others are widely dispersed; and many 

 change their abode at certain seasons of the year, 

 and migrate to climates more congenial with 

 their temperament or mode of life, for a certain 

 period, than those which they leave. Many of 

 the birds of our own island, directed by a pecu- 

 liar and unerring i,nstinct, retire, before the com- 

 mencement of the cold season, to the southern 

 parts of Africa, und again return in the spring. 

 The causes generally assigned for migration are, 

 either a defect of food, or the want of a secure 

 asylum for incubation and the nutrition of their 

 young. They generally perform their journeys 

 in large companies; and, in the day, follow A 

 leader, who is occasionally changed. 



VOL. in. NO. xvi. B 



