COOPER'S HA WK. 349 



by, carrying a fine rifle. He is a good marksman, so I 

 beckon him to my assistance. As I strike on the trunk of 

 the tree the bird leaves the nest, and my friend takes her 

 on the wing. Down she comes, so gradually that she almost 

 appears as if alighting, and skimming aloAg near the ground 

 for some distance, finally drops, squealing loudly enough 

 to alarm the whole feathered tribe in the neighborhood. 

 As I approach her, she defends herself with the heroism of 

 a true Hawk. The bullet has passed through her thigh, 

 shattering the bone thoroughly, and the two outer pinions 

 of one wing are cut away. But why should this simple 

 shattering of the thigh bring down so strong a bird so 

 readily ? The explanation is to be found in the peculiar 

 anatomy of the bird. In 1761, Peter Camper, a distinguished 

 Dutch anatomist, discovered that the cavities in the bones 

 of birds, which Gabbe had already observed to contain no 

 marrow, were in direct communication with the lungs, and 

 so participated in respiration. In I'ZVi, John Hunter, the 

 great English comparative anatomist, verified the same in his 

 marvelous researches into the anatomy of birds. Extending 

 their investigations in the most able manner throughout the 

 entire class of birds, they discovered that " the air-cells and 

 lungs can be inflated from the bones, and Hunter injected 

 the medullary cavities of the bones from the trachea. If 

 the femur" — the thigh bone — ^^ into which the air is admitted be 

 broken, the bird is unable to raise itself in flight. If the trachea 

 be tied and an opening be made into the humerus"— the up- 

 per wing-bone — " the bird will respire by that opening for 

 a short period, and may be killed by inhaling noxious gases 

 through it. If an air-bone of a living bird, similarly per- 

 forated, be held in water, bubbles will rise from it, and a 

 motion of the contained air will be exhibited, synchronous 

 with the motions of inspiration and expiration. 



