BIRDS. 299 



The joints of the neck are not only numerous, but are made 

 to work on each other with great ease and freedom, and are 

 furnished with numerous projections, to which the muscles 

 are attached. Some of these are shown in the annexed figure 

 (Fig. 237). 



Fig. 237. SKELETON OF THE OSTRICH. 



For the vertehrae of the back a different arrangement is 

 required; strength, not flexibility, is the object; and, accor- 

 dingly, in most birds they are united together, and are 

 consequently immoveable. They thus serve not merely as 

 supports for the ribs, but have the solidity which is needful to 

 furnish points of support for the wings also. So beautifully, 

 however, are those structures modified, that in birds which 

 do not fly, the consolidation of the joints of the back-bone 

 does not take place, and some degree of movement is thereby 

 secured. 



