HOOPER. 



197 



The cylindrical tube of the trachea or windpipe passes 

 down the whole length of the long neck of the bird, ip- 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, from 

 whence the two long bronchial tubes go off, one to each 

 lobe of the lungs. This singular structure will be further 

 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 insertion is not, however, so consi- 

 derable in females or young males. 



