Atn-AT^SRT.S OF inKDS. 17 



wiug, down the tliigh, and ul<o into the cavity of the hndj- ; hut tlio right side was not 

 in tlie least affected. The jjipe at the trachea being now removed, the air produced a 

 similar effect on the hirynx, but not so loud. Still suspecting that thoj'o was a communi- 

 cation between the sides by means of some valvular aj^paratus, the right side was sub- 

 jected to the same experiment ; but the result negati\'cd the expectation, the effect 

 produced being similar in every respect. 



" From a repetition of these experiments," says Colonel Montague, " it became evident 

 that there was a communication between the lungs and the cellular membrane that 

 covcM's the greater part of the body, as well as with the whole cavity of the body, but 

 that, by reason of some valvular contrivance, the skin coidd not be artificially inflated 

 through the lungs, although air woidd readily pass in a contrary direction. It is also 

 clear that there is no communication between the two sides." 



il. Tachard mentions the wouudiuQ' of a larse bird ; and, on its dissection, be found 

 imder tbe fleshy panicles \-ery delicate nu>mbranes, which (>uveloped the whole body. 

 Folding differently, they formed many considerable pouches, particularly between the 

 thighs and the belly, between the wings and tbe ribs, and under the craw. Some were 

 so ■wide as to admit the two fingers ; and these great pouches divided into many little 

 ducts, which perpetual subdivision ran into an endless multitude of ramifications, whicb 

 were perceptible only by the bubbles of air which inflated them ; so that, on pressing the 

 body of this bird, a little noise was heard like that prodticed by pressing the membra- 

 nous parts of an animal that has been inflated. By the assistance of the probe and 

 blowing, the comminiication of these membranes with the lungs was discovered. 



The structure so admirabh' adapted to render birds light and buoyant is thus happUy 

 described by Sir Charles Bell : — - 



" First, it is necessary that birds, as they are buoyed in the air, be specifically lighter; 

 secondly, the circumference of their thorax must be extended, and the motion of the ribs 

 limited, that the muscles of the Avings may have sufficient space and firnuiess for their 

 attachment. Both these objects are attained by a modification of the apparatus of 

 breathing. The lungs are hij^hly vasciilar and spongy, but they ai'e not distended with 

 air. The air is dra^^^^ through their substance into the large canity common to the 

 chest and abdomen ; whilst the great office of decarbonization of the blood is securely 

 performed, advantage is taken to let the air into all the cavities, even into those of the 

 bones. 



" The weight of the body being a necessary concomitant of muscidar strength, we see 

 why birds, by reason of their lightness, as well as by the conformation of their skeleton, 

 walk badly. And, on the other hand, in observdng how this Hghtness is adapted for 

 flight, it is remarkable how .small an addition to their body will prevent them rising on 

 the wing. If the griffon-\Talture be frightened after his repast, he must disgorge before 

 he flies ; and the condor, in the same circumstances, is taken by the Indians, like a 

 quadruped, by throwing the lasso over it. It is interesting to notice the relations of 

 great fimctions ia the animal economy : birds are oviparous, because they never coidd 

 have risen on the wrag had they been viAaparous ; if the full stomach of a carnivorous 

 bird retard its flight, we perceive that it could not have carried its young. The light 

 body, the quill-feathers, the bill, and the laying of eggs, are all necessarily connected. 



" As every one must have observed, the breast-bone of bu'ds extends the whole length 

 of the body ; and owing to this extension, a lesser degree of motion suffices to respiration ; 

 so that a greater surface, necessary for the lodgment and attachment of the muscles 

 of the wings, is obtained, whilst that surface is less disturbed by the action of breathing, 

 and is more steady. Another peculiarity of the skeleton of the bird, is the consolidation 

 of the vertebrne of the back ; a proof, if any were now necessary,- "that the Avhole system 

 of bones conforms to that of the extremities, the firmer texture of the bones of the trunk 



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