﻿EXTERNAL ANATOMY. TOES. 119 



it first appears only as a posterior scale, double the size 

 of the others. As the bird increases in age, so does 

 this scale increase in size and elevation, until it finally 

 becomes a solid acute spur. We pass over several other 

 variations of the tarsal scales, as seen in different groups, 

 and now proceed to other parts of the legs. 



(109.) The Toes of birds, by their leading varia- 

 tions, furnish the primary characters by which the whole 

 class is divided into orders, and the subordinate modi- 

 fications of their structure indicate, for the most part, 

 natural groups. In this respect they consequently de- 

 serve even more attention than the tarsi. We have 

 already described the peculiarities of retractile, perch- 

 ing, walking, wading, and swimming feet, and shall 

 therefore at once proceed to enumerate their several 

 variations. The great majority of birds have four toes 

 to each foot, three of which are usually placed before, 

 and one, which is called the hallux, or hinder toe, is 

 placed in a backward direction. The exceptions to this 

 number of toes, and to their disposition, are compara- 

 tively few ; the most remarkable instances, as regards 

 the number, are found in the ostrich family (Struthi- 

 (midce). The toes of the ostrich are only two, one 

 large, the other small : this extraordinary structure, for 

 a bird, is in perfect harmony with its station in the 

 great scheme of creation, for it is by means of this 

 animal, half quadruped, half bird, that nature passes 

 from the feathered class to that of the mammalia ; and 

 yet, although the ostrich would appear absolutely de- 

 prived of all those powers which enable birds to escape 

 from their enemies, either by perfect wings or highly 

 developed toes, she has nevertheless made the ostrich, 

 with its two toes, one of the swiftest running birds in 

 creation. The cassowary, the emu, and the Ame- 

 rican rhea, have three toes upon each foot, but the 

 latter only has the vestige of a fourth, which merely 

 shows itself in the form of a tubercle ; but in the 

 Apternyx, or New Zealand emu, the most aberrant of 

 the ostrich family, we find the hinder toe, although 

 1 4 



