BIRDS. 



283 



The joints of tlic 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 musck's 

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

 {Fig. 237). 



Fig. 237.— Skeletoh of thb Ostrich. 



For the vertebrje of the back a different arrangement is 

 required ; strength, not iiexibihty, is the object ; and, accord- 

 ingly, in most birds they are united togetlier, and are 

 consequently immovable. They thus serve not merely as 

 supports for the ril)S, 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. 



