G2 ORGANS OP BREATHING. 



supposed to have been carried away by a fox, when, 

 at the expiration of three weeks, it was discovered 

 alive ; for a few days it continued in a weak state, 

 but gradually resumed its strength. 



Having taken a short view of the frame-work and 

 internal construction of a bird, with reference to the 

 disposal of its food, we shall next consider some 

 other of the vital functions, commencing with those 

 of breathing and voice. The lungs of men and 

 animals occupy, as is well known, a large portion 

 of the chest, whereas, in birds, the space occupied 

 is not only much smaller, but the lungs themselves 

 are of a more firm and compact texture. At the same 

 time they are most plentifully supplied with air- 

 cells, communicating with other cells, profusely dis- 

 tributed over every part of the system, by which 

 their bodies are in a manner blown up and rendered 

 buoyant ; a considerable portion of the skeleton 

 moreover, as we have shown, being formed into re- 

 ceptacles for this light and elastic fluid, of which 

 birds partake in so much greater a degree than most 

 other parts of the creation. In fact, a bird, destined 

 as it is to live in air, may be almost called an abso- 

 lute air-vessel, so completely does air fill up and 

 circulate throughout its whole frame. While men 

 and other land animals breathe in air through the 

 nostrils alone, a bird respires through a variety of 

 other channels. A wounded Heron was observed 

 to live a whole day, breathing solely through a 

 broken portion of the wing-bone*. Other experi- 

 ments have confirmed the fact ; the fractured portion 

 of a bone that had been separated, when immersed 



* See Linncean Transactions, vol. xi., p. 11 



