BAT. 381 



office of a real wing. The bat flies with perfect ease, even 

 while carrying along with it one or two of its young: it is 

 not, however, fitted for very long flights. 



The conformation of the skeleton is adapted to this new 

 and important function. The chest is broad and capacious 

 to admit of free respiration while the animal is flying, and 

 to afi'ord ample space for the attachment of the large mus- 

 cles which have become necessary. The scapulae (s) are 

 large, and of a singular form, and they are kept at a consi- 

 derable distance asunder by the expanded chest: their cora- 

 coid processes are also large, and extend in the direction of 

 the sternum. The clavicles (c) are of enormous size and 

 length, being larger than either the scapula or the sternum, 

 and remarkably curved in their shape. The sternum is 

 much developed, extending laterally, and having a project- 

 ing crest along the middle of its lower surface. The hu- 

 merus (h) is strong, but short; apparently in order to avoid 

 the danger of its being snapped asunder by the violent ac- 

 tions of the pectoral muscles, had it been longer. As the 

 leading object of the structure is to give power to the wing, 

 there was no necessity for the rotatory motion of the bones 

 of the fore-arm; and accordingly we find them consolidated 

 into one (r;) or rather no part of the ulna is developed, ex- 

 cept the process of the olecranon, or elbow, which has be- 

 come soldered to the radius. 



These advantages in the construction of the fore extremi- 

 ties are obtained at the expense of the hinder, which are too 

 feeble to support the weight of the body in the upright posi- 

 tion required for walking, in consequence of the centre of gra- 

 vity being between the wings. On a level plane, indeed, the 

 bat can advance only by a kind of crawling or hoj^ping motion. 

 The whole anterior half of the trunk is much more fully de- 

 veloped than the posterior half, which appears as if it had 

 been checked in its growth. The pelvis (p) is of diminutive 

 size, compared with the rest of the skeleton : the pubic bones 

 are lengthened backwards, and are joined merely at a small 

 point. The whole posterior limb is short, the femur (f ) com- 



