11 



and he thought it probable that the wing-bones only of the swans, 

 geese and ducks would be found to be hollow. 



After John Hunter's paper in the sixty-fourth volume of the 

 London Philosophical Transactions, 1774, being "An Account of 

 certain receptacles of air in birds, which communicate with the lungs 

 and are lodged among the fleshy parts. and in the hollow bones of 

 these animals," Camper published a letter (vol. iii. p. 474) claiming 

 the discovery three years before Hunter had spoken of it. 



Hunter, in the paper above mentioned, appears to have confined 

 his observations to a few birds, and his three quoted experiments for* 

 the purpose of showing that a bird may breathe through apertures 

 made in the humerus or air-sacs, are very inconclusive. The birds 

 he speaks of are the ostrich, the common fowl, the woodcock, peli- 

 can and canary. The chief object of the paper was to show that the 

 air-sacs and bones are appendages to the lungs. The essays of these 

 great anatomists, of which I have given a brief outline, will well 

 repay perusal ; and if many subsequent writers upon the subject had 

 depended upon their own observations, the prevailing error " that the 

 hones of a bird are filled with air," would not have occurred. 



In Cuvier's 'Animal Kingdom' is the following:-—" The air-cavities 

 which occupy the interior of their body, and even (usually) super- 

 sede the marrow in their bones, increase their specific lightness." 



Milne-Edwards, in his 'Elemens de Zoologie,' p. 504, says, "In 

 general, air is found in great abundance in the bones of the members 

 most employed in locomotion. In the ostrich, for example, the air- 

 cells in the femur have a remarkable development." 



The late Mr. Yarrell, whose recent death we all so much deplore, 

 does not in his work on British Birds speak of the bones ; but in 

 his 'British Fishes' (Introduction, p. 21), he says, in alluding to 

 the air-bladder, " The analogy to the air-cells in birds, and the pas- 

 sage of air from thence into the bones of the limbs, is too obvious 

 to be unobserved, and will give interest to further investigation." 

 So that Mr. Yarrell' s impression evidently was, that the limb-bones 

 of birds were supplied with air. 



Mr. Rymer Jones, in his ' Organization of the Animal Kingdom,' 

 1855, p. 75, says, " Birds, in fact, breathe not only with their lungs, 

 but the vital element penetrates almost every part of the interior of 

 their bodies, bathing the surfaces of their viscera, and entering the 

 very cavities of their bones ; so that the blood is most extensively 

 subjected to its influence." 



In Carpenter's 'Comparative Physiology,' 1854, it is said, that 

 " Even the bones are made subservient to this function (respiration) ; 

 for though at an early period they possess a spongy structure, like 

 those of reptiles, and are filled with thin marrow, they subsequently 

 become hollow, and their cavities communicate with the lungs. In 

 the aquatic species, however, the original condition is retained through 

 life." And in his ' Manual for the Use of Students,' p. 386, it is 

 stated, that in most birds the bones are hollow. 



Professor Owen, in his article " Aves " in the ' Cyclopaedia of 

 Anatomy and Physiology' (vol. i. p. 343), remarks, "The singular 



