314 MAMMALIA AND BIRDS. 



vigorous action of the legs which is required in them. 

 In both, and more especially in the latter, it serves 

 more as a breast-plate or buckler for supporting the 

 anterior part of the bod}^, by reference to the spinal 

 column, and bj means of that to the legs, than as 

 the ultimate fulcrum of any sort of motion ; and in 

 these birds the scapular bones, b}^ means of which 

 the anterior part of the sternum is supported, or 

 rather by means of which it is suspended, are more 

 produced, and have their forms better adapted for a 

 firm imbedment among the muscles of the back, 

 than in habitual llyei-s. So marked does this character 

 become, that in the ostrich tribe, which, as they do 

 not require the furcal bone to keep the heads of the 

 scapulars asunder, have it only in two rudimental 

 processes, the coracoids and scapulars have much the 

 character and office of two hooks, which, taking hold 

 by means of their imbedment in the flesh, bear up 

 the anterior part of the sternum. 



This enlarged and basket or boat-shaped sternum, 

 together with the coracoid bones, are therefore to 

 be regarded as the most typical part not only of the 

 skeleton of birds, but of their whole organisation. 

 The form of the sternum varies much with the habits 

 of the different species ; but it is, in all cases, the 

 characteristic sternum of a bird, and in no species, 

 which has been examined, has it been found without 

 coracoids, though in those species where these do 

 little else than suspend the sternum they are united 

 into nearly one continued flat piece with the scapulars. 



It is to be regretted that, hitherto, there has been 

 no opportunity of completing this part of the series 

 by examining the sternal apparatus of the apteryx, 

 which, as the most wingless of the class, and as being, 

 from the structure of its feet, a bird of slow motion, 



