12 



extension of the respiratory into tlie osseous system was discovered 

 simultaneously by Uunter and Camper, and ably investigated by 

 them through the whole class of birds. It is stated that if the femur 

 into vrhich the air is admitted be broken, the bird shall not be able 

 to raiše itself in flight." He then quotes from Hunter's experi- 

 ments before alluded to. 



Professor Owen goes on to say, that " the proportion in which the 

 skeleton is permeated by air varies in different birds. In the pen- 

 guins he found no air in the bones. The struthious birds have all 

 air admitted into the cavities, except the humeri, tihiee and distal 

 bones of the legs, which retain their marrow. With the exception 

 of the woodcock, all birds of fiight have air admitted into the hu- 

 merus. The pigeons, with the exception of the crown pigeon, have 

 no air in the femur, which retains its marrow. In the owls also the 

 femur is filled with marrow, but in the diurnal birds of prey, as in 

 almost all other birds of flight, the femur is filled with air. In the 

 pelican and gannet the air enters all the bones vs'ith the exception of 

 the phalanges of the toes. In the hornbill even these are permeated 

 by air." 



In his ' Lectures on Comparative Anatomy,' vol. ii. p. 34, nearly 

 the šame opinion is expressed, and the swifts and humming-birds 

 are said " to have air in every bone of the skeleton down to the pha- 

 langes of the clavvs." 



I make no apology for these ąuotations, because they are essential 

 for the proper understanding of the matter. 



I have placed on the table a French and English partridge, a lark, 

 a šnipe, a sparrow, a starling, and the skeleton (in maceration) of a 

 swift {Cypselus apus), and it will be seen that in the three first- 

 named birds only do the humeri contain air ; the other bones are 

 filled with marrow ; in the remaining four birds the bones contain no 

 air : but I should observe that in two swifts before examined I found 

 the humeri hollow, the other bones fuU of marrow. I also exhibit 

 the bones of many birds that I have dissected ; among these are the 

 ostrich, jabiru, eagle, sparrow-hawk, \Veka-rail, green vFoodpecker, 

 and many of the femora and humeri of the smaller British birds, 

 nearly all of which are filled with marrow ; indeed there are no 

 apertures in the bones for the admission of air. 



To bring the ųuestion to a more practical bearing, I subjoin a list 

 of birds recently dissected (most of them shot by myself), in which 

 I have examined the bones of the extremities to ascertain the pre- 

 sence or absence of air, and in this communication 1 think it better 

 to include only British birds. 



Sparrow Hawk. F. nisus. Common Duok. 



Magpie. C. pica. Velvet Scouter. O./usca. 



Jackdaw. C. monediila. Common Fowl. 



"VVoodpigeon. C. palumbus. Turkey. 



Turtle Dove. C. turtur. Partridge (English). P. cinerea. 



Sky Lark. A. arvensis. Partridge (French). P. ru/a. 



Green AVoodpecker. P, viridis. Bittern. B. stellaris. 



