[65] “On the Functions of the Air-cells and the Mechanism of Respiration in Birds,” by W. H. Drosier, M.D., Caius College.--Proc. Camb. Phil. Soc., Feb. 12, 1866. [66] “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.”--Phil. Trans., Lond. 1774. [67] According to Dr. Crisp the swallow, martin, snipe, and many birds of passage have no air in their bones (Proc. Zool. Soc., Lond. part xxv. 1857, p. 13). The same author, in a second communication (pp. 215 and 216), adds that the glossy starling, spotted flycatcher, whin-chat, wood-wren, willow-wren, black-headed bunting, and canary, five of which are birds of passage, have likewise no air in their bones. The following is Dr. Crisp’s summary:--Out of ninety-two birds examined he found “air in many of the bones, five (_Falconidæ_); air in the humeri and not in the inferior extremities, thirty-nine; no air in the extremities and probably none in the other bones, forty-eight.” [68] Nearly allied to this is the great gular pouch of the bustard. Specimens of the air-sac in the orang, emu, and bustard, and likewise of the air-sacs of the swan and goose, as prepared by me, may be seen in the Museum of the Royal College of Surgeons of England. The same may be said of the hollow bones,--some really admirable fliers, as the swifts, martins, and snipes, having their bones filled with marrow, while those of the wingless running birds alluded to have air. Furthermore and finally, a living bird weighing 10 lbs. weighs the same when dead, plus a very few grains; and all know what effect a few grains of heated air would have in raising a weight of 10 lbs. from the ground.