FLIGHT. 275 



" 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, while 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 adapt- 

 ed to this one object, the power of the wings ? 



" While the ostrich has no keel in its breastbone, 

 birds of passage are, on dissection, recognisable 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 lodgment for the pectoral 

 muscle, 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 con- 

 stitutes 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, 

 while the pectoral muscles of man are but a seven- 

 tieth 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 lives on the wing ; it eats, 

 drinks, and collects materials for its nest in flying, 

 and never rests but during darkness. If it be true 

 that birds, when migrating, require a wind that blows 

 against them, it implies an extraordinary power as 

 well as continuance of muscular exertion. 



" We see how Nature completes her work, when 

 the intention is that the animal shall rise buoyant 

 and powerful in the air : the whole texture of the 



