. The bird, its form and function . pple. The vocalchords and other adjuncts to the voice of mammalsare entirely absent in birds, not a single note or songbeing produced in the upperthroat. Passing down the neckfrom this orifice is the wind-pipe, which follows thecourse of the oesophagus, orfood canal, passes to oneside of the crop and be-tween the two branches ofthe wish-bone, and finallydivides into two equal partscalled bronchi, which carrythe air directly to the lungs. Comparison of the twotubes which traverse the throat and neck of birds shows them to be vpiy differentin appearance and st
. The bird, its form and function . pple. The vocalchords and other adjuncts to the voice of mammalsare entirely absent in birds, not a single note or songbeing produced in the upperthroat. Passing down the neckfrom this orifice is the wind-pipe, which follows thecourse of the oesophagus, orfood canal, passes to oneside of the crop and be-tween the two branches ofthe wish-bone, and finallydivides into two equal partscalled bronchi, which carrythe air directly to the lungs. Comparison of the twotubes which traverse the throat and neck of birds shows them to be vpiy differentin appearance and structure, and consideration of theirrespective functions gives us the key to this only occasion for the oesophagus to. open is to permitthe passage of food, and thus a limp, fleshy canal answersall requirements. The windpipe, on the contrary, mustalways be wide open, and not only this, but it must be keptopen no matter what the pressure upon it. In addition,it must be flexible, yielding to every motion of the neck,. Fig. 127.—Windpipe and oesophagus ofbird compared; the former always dis-tended; the latter soft and collapsed. i68 The Bird and elastic, in order to stretch and contract as the hirdreaches out or draws back its head. We find a most ingenious arrangement fulfilling allthese requirements. A series of bony rings is imbeddedin the wall of the trachea, beginning with that portion
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Keywords: ., bookauthorbeebewil, bookcentury1900, bookdecade1900, bookyear1906
