150 



ORGANS OP LOCOMOTION 



In birds, the pigeon, for example (fig. 164), there are but two 

 fingers (</), which are soldered, and destitute of nails ; and 

 the thumb is rudimentary. 



28-4. The arm of the turtle (fig. 166) is peculiar in having, 



Fig. 165 



Fig. 166. 



Fig, 167. 



besides the shoulder-blade (), the coracoid bone and the cla* 

 vicle; the arm-bone (6) is twisted outwards, as well as the bones 

 of the fore-arm (c, d\ so that the elbow, instead of being be- 

 hind, is turned forwards ; the fingers (g) are long, and widely 

 separated. In the sloth (fig. 165), the bones of the arm (b] and 

 fore-arm (c,d] are very greatly elongated, and at the same time 

 very slender ; the hand is likewise very long, and the fingers (g} 

 are terminated by enormous non-retractile nails. The arm of 

 the mole (fig. 167) is still more extraordinary. The shoulder- 

 blade (), which is usually a broad and flat bone, becomes very 

 narrow ; the arm-bone (b), on the contrary, is contracted so 

 much as to seem nearly square, the elbow projects backwards, 

 and the hand (e, f, g] is excessively large and stout. 



285. In fishes, the form and arrangement of the bones is so 

 peculiar, that it is often difficult to trace their correspondence to 

 all the parts found in other animals ; nevertheless, the bones of 

 the fore-arm (c, d] are readily recognized. In the cod (fig. 1 68), 



Fig. 168. 



there are two 

 flat and broad 

 bones, one of 

 which, the 

 ulna (d), pre- 

 sents a long 

 point, anteri- 



