THE SPINAL COLiraiN OF BIRDS. 147 



grebe there are eighteen or nineteen; in the 

 great penguin, thirteen; in the sparrow, nine. 

 In the waders, swans, and other very long- 

 necked birds, the cervical vertebrae are them- 

 selves of a far more elongated form than in 

 birds with shorter necks. The cervical ver- 

 tebrae are united together in a simple manner; 

 there is no elastic cushion between the bodies 

 of each, but they are connected by articu- 

 lating facets, (one on each side,) and at each 

 inclosed by a capsule or membrane ; these 

 opposing facets have, however, a little smooth 

 cartilage between them in order to facilitate 

 their movements. "We have spoken of the 

 neck of birds as constituting a sort of many- 

 jointed arm; and, like the arm, it subserves 

 another purpose besides that for which it is 

 primarily designed — it acts as a balancer. 

 We have seen, from the position of the hip- 

 joint, the tendency of the body to fall forward. 

 This tendency may be partially counteracted 

 by drawing back the head. In terrestrial 

 birds, as the fowl and turkey, the head is 

 ordinarily drawn considerably back, as they 

 move quietly about. It is so in the duck also-; 

 birds with long legs and necks — as the heron, 

 the stork, the Marabou crane, and others — stan'' 



