240 FACULTIES OP BIRDS. 



bird, is the consolidation of the vertebrae of the back ; 

 a proof, if any were now necessary, that the whole 

 system of bones conforms to that of the extremities, 

 the firmer texture of the bones of the trunk being a 

 part of the provision for the attachment of the muscles 

 of the wings. The ostrich and cassowary, which are 

 rather runners than fliers, have the spine loose. 



" The vertebrae of the back being fixed in birds, 

 and the pelvis reaching high, there is no motion in 

 the body ; indeed, if there were, it would be inter- 

 rupted by the sternum. We cannot but admire, 

 therefore, the composition of the neck and head, and 

 how the extension of the vertebrae, and the length 

 and pliability of the neck, whilst they give to the 

 bill the office of a hand, become a substitution for the 

 loss of motion in the body, by balancing the whole, 

 as in standing, running, or flying. Is it not curious 

 to observe how the whole skeleton is adapted to this 

 one object, the power of the wings? 



" Whilst the ostrich has no keel in its breast-bone, 

 birds of passage are, on dissection, recognizable by the 

 depth of this ridge of the sternum. The reason is, 

 that the angle formed by this process, and the body 

 of the bone, affords lodgement for the pectoral mus- 

 cle, the powerful muscle of the wing. In this sketch 

 of the dissection of the swallow, there is a curious 

 resemblance to the human arm ; and we cannot fail 

 to observe, that the pectoral muscle constitutes the 

 greater part of the bulk of the body. Borelli makes 

 the pectoral muscles of a bird exceed in weight all 

 the other muscles taken together, whilst the pectoral 

 muscles of man are but a seventieth part of the 

 whole mass of the muscles. And here we see the 

 correspondence between the strength of this muscle 

 and the rate of flying of the swallow, which is a mile 

 in a minute, for ten hours every day, or six hundred 

 miles a day. Mr. White says truly, that the swift 



