BIRD. 



439 



ligaments may not be stiffened and rendered unfit for 

 action by the cold. 



There is considerable freedom of motion laterally 

 in the toes of these clutching feet. When they are 

 employed in violent or excited action, the four claws 

 are nearly equi-distant, and all their points are 

 directed toward the same centre, so that in whichever 

 direction the prey writhes, it always runs itself more 

 and more upon the point of a portion of the claws, 

 and the trenchant edges at the same time tear and 

 mangle its flesh. The same position of the toes 

 enables the birds to perch on the points of rocks and 

 other places of observation, from which they can dis- 

 cover their prey. But such feet are not well adapted 

 for walking ; and when the birds have to change their 

 place even for a short distance upon the ground, they 

 always raise or move the wings. Thus, though the foot 

 of birds of prey is used for various purposes upon the 

 ground, it cannot be regarded as a foot well adapted 

 for any kind of progressive motion. The feet of 

 ravens, and several other omnivorous birds, partake 

 a little of this character, and hence they hop rather 

 than walk, and partially raise the wings to balance 

 themselves. 



Ground Feet. Birds have so many different 

 actions upon the ground, and the ground itself offers 

 so many different kinds of surface, that it is not very 

 easy to reduce the feet to any thing like an explicit 

 system. If the bird is a swift runner, the tarsi are 

 long, the thigh bones articulated a little farther for- 

 ward, and their action more free ; but then the termi- 

 nation of the foot, which is usually attended to in the 

 descriptions of the feet of birds, varies with the 

 ground on which it is to be used, and this again 

 causes a modification of the other parts of the leg. 

 If the back toe is long, and articulated at the same 

 level with the other toes, then the foot must be 

 placed farther forward, in order that the axis of the 

 body may be carried horizontal, than when the hind 

 toe is weak, or wanting, or articulated higher on the 

 tarsus than the other toes. Feet also combine other 

 actions, such as scraping in the earth, or swimming 

 with their action of progressive motion upon land, 

 and this farther embarrasses us in our attempts to 

 classify them ; so that, without writing almost as 

 many volumes as there are kinds of feet, little else 

 can be done than simply to mention the description 

 of surface and motion, and notice the form of the foot. 



For swift motion over arid surfaces, covered with 

 dry sand, the foot of the ostrich is best adapted. 



Ostrich. 

 This foot has only two toes, both thick and strong, 



the inner short, and without any claw ; the outer 

 longer, and furnished with a broad blunt one. The 

 tarsus is very thick as well as long, and the muscles 

 on the tibia are large, and extend'as far down as the 

 tarsal joint. The joints have little lateral motion, 

 but the progressive motion is extensive, and the foot 

 is lifted clean and high above the ground. As the 

 ostrich is the swiftest of all running bird?, we must 

 conclude that this is the best running foot upon dry 

 surfaces; but it cannot be considered as the normal 

 foot of the group, for the others have three toes, and 

 the cassowary has a long nail on the inner one, and 

 the tarsi feathered a great way down. 



The swift-footed birds which frequent the dry 

 shores and heaths, but which have occasionally to 

 pass over surfaces more or less humid or soft, have 

 three toes before, and none behind in some species, 

 a mere rudiment in others, but not a very large toe 

 in any. They have the middle, or outer toe, more or 

 less united by membrane at the base, according as 

 the surface on which they generally run is more or 

 less soft. They are all birds of flight, not having the 

 muscles concentrated on the hind legs, like the 

 ostriches, and their legs are in general slender ; and 

 though many of them run fast, the tonat take com- 

 paratively as long strides as the ostrich tribe. The 

 loot of the common plover is nearly an average 

 example. 



The bustards form a sort of connecting link between 

 the " stilt" birds, which run upon dry and naked 

 places, and the gallinidse, which frequent richer and 

 softer ground. They can rly, and flight is their means 

 of escape from serious danger, and also of transport 

 on their longer journeys ; but in ordinary they walk 

 or run. The following is the form of the foot, three 

 toes before, with short membranes at the bases, and 

 a sort of cartilaginous heel, but no back toe. 



Birds which frequent very soft surfaces, have gene- 

 rally the toes larger, and bordered more or loss with 



