334 STERNUM OF THE SWIFT. 



means of judging will be still more complete and 

 satisfactory. 



The sternum of the falcon is firmer and more 

 developed in the anterior part than either of the other 

 two, but it is shorter, narrower at its posterior edge, 

 not so hollow, and weaker from the holes at the 

 angles. That of the eagle is larger backwards, more 

 concave, and the holes are nearly obliterated, but still 

 the anterior part of it is broadest. That of the swift 

 has the posterior part broadest, and the angles have 

 no holes. Thus in the falcon the whole strength of 

 the sternum is concentrated upon that part on which 

 the grand flying muscles are inserted ; and the more 

 perfect arch and uniform strength of the furcal bone 

 harmonise, and render the whole sternal apparatus 

 the most efficient for powerful flight. There is ac- 

 cordingly no bird which has the same desperate rush 

 as the falcon, and that rush is performed almost ex- 

 clusively by the effort of the wings, and with com- 

 paratively little momentum from gravitation. Indeed 

 a force or momentum produced by gravitation would 



