292 



THE ANATOMY OF VERTEBEATED ANIMALS. 



Fis. 85. 



tlu-ee digits in tlie manus, whicli answer to the pollex and the 

 second and third digits of the pentadactyle fore limb; and 

 the metacarpal bones of these digits are ankylosed together. 

 As a rule, the metacarpal of the pollex is 

 much shorter than the other two ; that of 

 the second digit is strong and straight, 

 that of the third is more slender and 

 bowed, so as to leave an interspace be- 

 tween itseK and the second, which is 

 often filled up by bony matter. The 

 pollex has two phalanges, and the second 

 of them is, in many birds, pointed, curved, 

 and ensheathed in a homy claw. The 

 second digit has three phalanges, and 

 the terminal phalanx is similarly pro- 

 vided with a claw in simdry birds. In 

 the ostrich, both the pollex and the second 

 )■» digit are unguiculate. The third digit 

 never possesses more than one or two 

 phalanges, and is always devoid of a 

 claw. 



It is a singular circumstance that the 

 relative proportions of the humerus and 

 the manus should present the most 

 marked contrast in two groups of birds, 

 which are alike remarkable for their 

 powers of flight. These are the Swifts 

 and Humming-birds, in which the hu- 

 merus is short and the manus long ; and 

 the Albatrosses, in which the humerus is 

 long and the manus relatively short. 



In the Penguins, the pollex has no 

 free phalanges, and its metacarpal bone 

 seems to be ankylosed with that of the 

 second digit. The third metacarpal is 

 slender and straight. The bones of the 

 manus are singularly elongated and 

 flattened. 



Fig. 85.— The radius 

 (/■) ; ulna («) ; ra- 

 dial and ulnar car- 

 pal bones (/, u') • 

 with the three di- 

 gits (i., ii., iii.), of 

 the right fore limb 

 of a Fowl. The 

 terminal pha- 

 langes of both the 

 first and the se- 

 cond digits were 

 incomplete in the 

 specimen figured. 



