no 



cellular reservoirs of air, as in reptiles in gene- 

 ral ; but, she has made their windpipe of an im- 

 mense length, and laid it in folds behind their 

 breast-bone, so that sinking their heads into the 

 water with this full of pure air, they can support 

 respiration for a long time upon its contents 

 alone. This structure is beautifully seen in the 

 male crane. The ribs of birds, by the motions 

 of which the common cavity of the chest and ab- 

 domen for they, like reptiles, are destitute of a 

 midriff is expanded, and air drawn into the 

 lungs, and, through the lungs, into almost the 

 whole body, are unprovided with elastic carti- 

 lages, such as are met with in mammiferous 

 animals ; but they have, instead of them, perfect 

 joints about midway between the spine and 

 breast-bone, by which, when bent, the general 

 cavity is constricted, and, when straightened, it 

 is dilated, the breast-bone either approaching or 

 receding from the spine, according to the angle 

 which these joints form. 



In the" mammalia, as well as in birds, the 

 lungs are fleshy, and each is, in like manner, 

 bound down to the spine ; there are, however, 

 no longer any external orifices, by which air is 

 transmitted thence to other parts of the body. In 

 the cetaceous mammalia, however, or those that 

 live in water, the lungs are commonly continued 

 for some space down the spine, so as to remind 

 us of the air-bladder of fishes. In these tribes 

 also the nostrils, in which the wind-pipe termi- 

 nates, open, not near the mouth their usual 



