o66 THE MECHANICAL FUNCTIONS. 



capable of breaking a man's leg ; and a similar 

 blow from an eagle has been known to be 

 instantly fatal. The bat is the only instance, 

 among the mammalia, where the sternum pre- 

 sents this peculiar caiinated, or keel-like shape : 

 and the purpose is evidently the same as in the 

 bird.* 



The scapula is generally a small and slender 

 bone. The coracoid bone (k) is largely deve- 

 loped, and assumes much of the appearance of a 

 clavicle. t But the real clavicles (c) are united 

 below, where they join the fore part of the 

 sternum, appearing as one bone, which, from its 

 forked shape, has been denominated the furcular 

 bone. In the fowl it is commonly known by the 

 name of the merry-thought. This bone, placed 

 at the origin of the wings, and stretching from 

 the one to the other, is of great importance as 

 constituting a firm basis for their support, and 

 for securing their steadiness of action ; and being, 

 at the same time, very elastic, it tends to restore 

 them to their proper situations, after they have 

 been disturbed by any violent impulse. 



* Notwithstanding the great moditication the sternum lias 

 received in the bird, when compared with its form in the tortoise 

 and the quadruped, we may still trace the same nine elements 

 entering into its composition, though developed in very different 

 proportions. 



+ Many have considered this bone as being the clavicle, and 

 have regarded the furcular bone as a new bone, or supplemen- 

 tary clavicle : but all the analogies of position and of develope- 

 ment are in favour of the views stated in the text. 



