10 



this matter in consequence of hearing the following statement by 

 Professor Owen, in one of his Lectures at the College of Surgeons, 

 on the Vertebrata, of which I took notes at the time. The lec- 

 turer, to show the permeability of the bones of birds to air, said, 

 " that a friend of his saw a man driving sea-gulls near Boulogne, and 

 being surprised that the birds did not fly, he inquired the reason, and 

 was told by the man that their thigh-bones had been perforated to 

 let out the air ; " and in further corroboration of this, Professor 

 Owen said, " every sportsman knows that when the legs of a par- 

 tridge are broken, it falls from the same cause." 



I knew that this latter statement was an error, for two reasons — 

 first, because a partridge does not fall when its legs are broken ; and, 

 secondly, and especially, because the thigh-bones of this bird do not 

 contain air. In my dissections of the gulls I had not examined the 

 thigh-bones ; but to my surprise on investigating this matter, I 

 found in all specimens afterwards dissected, that neither the humeri 

 nor the femora contained air, but were filled with marrow. I next 

 began to ask myself whether the presence of air in the femora of 

 most birds would not act as an impediment to their flight, by dimi- 

 nishing the strength of the bone, and more particularly by depriving 

 them of that weight and ballast which might be essential to their 

 aerial progress 1 I knew, moreover, that most of our bats (the bones 

 of which are free from air) could keep on the wing for many hours, 

 some of them carrying their young, whilst probably the sparrow, 

 robin, wren, partridge, and many other birds, could not sustain a 

 continuous flight for five minutes. I next discovered that in many 

 specimens of the common fowl, a bird that had scarcely ever topped 

 a brick wall, the humerus was hollow ; but in other birds of long 

 flight that I examined at the same time, including the snipe, curlew, 

 and many birds of passage, that none of the bones of the extremities 

 contained air. Before proceeding further with the investigation, I 

 consulted several modern writers upon the subject, and I subjoin ex- 

 tracts from their works for the purpose of showing the prevailing 

 opinion upon the matter. It was not till this morning, after the 

 above was written, that I consulted the essays of Camper and Hun- 

 ter, and it will perhaps be more methodical to quote these anatomists 

 before the others. 



The first writer I find upon the subject is Camper, ' (Euvres 

 d'Anatomie Compare'e,' Paris, 1803, vol. hi. p. 460. The paper was 

 presented to the Haarlem Academy, and he calls the discovery one 

 entirely new, " that nearly all the bones of birds are filled with air by 

 respiration ;" he entitled it a discovery, because he knew of no author 

 who had indicated the same thing. Marsighni had spoken of the 

 wing-bones of the pelican as very light and hollow, but he did not 

 allude to air, nor the manner in which it entered the cavity. The 

 first observations (February 1771) were made on the sea-eagle, owl, 

 maccaw, turkey, black-cock, and common fowl. The humeri and 

 femora were perforated, and the air-sacs and lungs inflated through 

 the apertures. He came to the conclusion (verified by finding that 

 the thigh- and wing-bones of a sparrow contained marrow) that all 

 high-flying birds had the bones of the extremities filled with air ; 



