314 



ANATID^. 



The internal distinctions of the Whooper are more con- 

 spicuous than those which have been referred to as external, 

 and of the former, the organ of voice furnishes the most 

 valuable and decisive characters. This peculiarity was 

 known to Willughby, but it was previously noticed by Sir 

 Thomas Browne, who mentions " that strange recurvation of 

 the windpipe through the sternum." 



The cylindrical tube of the trachea or windpipe passes 

 down the whole length of the long neck of the bird, in the 

 usual manner, but descends between the two branches of the 

 forked bone, called the merrythought, to a level with the 

 keel of the breast-bone or sternum. The keel of the breast- 

 bone is double, and receives between its two plates or sides, 

 the tube of the trachea, which, after traversing nearly the 

 whole length of the keel, turns suddenly upon itself, passing 

 forwards, upwards, and again backwards, till it ends in the 

 vertical bone of divarication, whence the two long bronchial 

 tubes go off, one to each lobe of the lungs. This singular 

 structure will be understood by a reference to the vignette 

 below, where a portion of one side of the keel is removed to 

 show the convoluted tube within. The depth of the inser- 

 tion is not so considerable in females or young males. 



