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Chapter XV. 



THE SKELETON OF THE FOWL. Gallus Domesticus. 



The fowl's skeleton is, on account of its larger size, more 

 convenient for study than that of the pigeon. The differences 

 between the two are of but slight importance, and the fol- 

 lowing description will practically apply to either. 



The bird's skeleton consists essentially of the same parts 

 as the rabbit's, but presents certain special characteristics, of 

 which the more important are : (1) The great lightness of 

 the bones, many of which contain large air cavities ; (2) the 

 extensive fusion of primitively distinct bones with each 

 other during development ; (3) the modifications in the 

 limb-girdles and limbs, fitting birds for bipedal locomotion 

 and for flight. 



As in the case of the rabbit's skeleton, the names of the 

 membrane-bones are printed in italics, those of the cartilage- 

 bones in thick type. 



I. THE AXIAL SKELETON. 



The axial skeleton, as in other vertebrates, is divisible 

 into skull and vertebral column. 



A. The Vertebral Column. 



As compared with the rabbit's, the vertebral column of 

 the bird is distinguished by (1) the great length and flexibility 

 of the neck, the cervical portion being nearly equal in length 

 to the whole of the rest of the column ; (2) the rigidity of the 

 thoracic and abdominal portions of the column, owing to the 

 fusion of their component vertebrae ; (3) the great length of 



