MEMOIR OF CAMPER. 45 



in his excellent discourse on the nature of birds, 

 but he says nothing concerning this extraordinary 

 adaptation of structure. 



" There was brought me on the 1st of February 

 1771 a great sea-eagle, of which I made a minute 

 dissection. Among other parts, I prepared one of 

 the thigh-bones, chiefly to shew its cavity, and the 

 fibres which support the bony plate in its interior. 

 I expected to find marrow, but was disappointed, 

 discovering nothing but the periosteum, and a large 

 vein, and some traces' of air. Astonished at this 

 peculiarity, I took a sketch of it, and instantly went 

 to examine the skeletons of a common eagle, an ara, 

 and an owl. I found a great foramen in the upper 

 part of the thigh-bone of the eagle, but no appear- 

 ance of one in the other two birds ; but I at the 

 same time discovered a foramen near the head of the 

 great bone of the wing, in the whole of my skele- 

 tons of birds. This was true also with the recent 

 sea-eagle, and hence the first step of my reasoning ; 

 there is a foramen in the leg bone, and air in it; 

 there is also a foramen in the wing bone, and pro- 

 bably there is air in it also, though, as yet, 1 know 

 not whence it comes. It happened that at this time 

 I had an owl which had just died : I drilled a small 

 hole in the principal bone of its wing ; to this I ap- 

 plied a blowpipe, and found, to my great delight, 

 hat, in blowing through it, I inflated the whole of 

 the chest, and also of the abdomen ; after this, the 

 air made its escape by the windpipe I then re* 



