OBSERVATIONS ON THE GANNET. 187 



peculiar circumstances, in order to support life 

 with ease, without continued respiration, as in 

 long submersion. But in order to derive the most 

 ample advantage from so curious a conformation, 

 a free circulation of the confined air must be car- 

 ried on through the lungs, in order to supply vital 

 energy, by the absorption of oxygen .which is 

 absolutely necessary to the existence of animals ; 

 thus, by passing and repassing through the lungs, 

 the duration of submersion may be greatly ex- 

 tended, beyond what would result from simple 

 pulmonary inspiration. 



From the attachment of the lungs of a bird to 

 the ribs and backbone, they are not capable of 

 much distension, consequently can contain a very 

 small portion of air ; if, therefore, some extraor- 

 dinary, or peculiar means, different from what is 

 found to obtain in the class Mammalia, had not 

 been given it, respiration must have been ex- 

 tremely quick and laborious, to supply the blood 

 with that vital principle which is furnished by the 

 decomposition of the air in these organs. Besides, 

 by so small a portion of air as the lungs of a bird 

 would alone contain, their voice must have been 

 so extremely weak, as to be wholly useless to 

 many, whose active, restless, and migratory life 

 renders it absolutely necessary that their cry 

 should be strong, in proportion to quick transpor- 

 tation from one place to another, in order that 

 those of the same species should discover each 



