44 PLUMAGE OF THE LEG. 



prongs have such mutual obliquity, that when the toes are brought forward, 

 at right angles or thereabouts with the tarsus, they sjoread themselves iu 

 the action, and the open foot, with its diverging toes, are pressed on the 

 ground or against the water; and when the toes are bent around in the other 

 direction, they close together more or less parallel with each other, besides 

 being bent or flexed, each one at its several nodes. The mechanism is best 

 illustrated in the swimmers, which must present a broad surface to the water 

 in giving the backward stroke, and bring the foot forward closed wi{h only 

 an edge opposed to the water. It is carried to such extreme in the loon, 

 that the digit marked 2t in the figure lies below and behind 3<, as there 

 shown ; in most birds with the foot in much the same position relative to the 

 tarsus, 2< Avould appear above 3< (compare other figures of feet). It is 

 probably least marked in birds of prey, that clutch with all the toes spread. 

 The individual toe joints are all simple hinges. 



(b.) In ordinary hopijing, walking, perching, etc., only the toes rest upon 

 or grasp the support, and c is more or less perpendicularly above d. This 

 resting of the toes is complete for all the anterior ones ; for the hind toe it 

 varies according to the position and length of the latter from complete 

 resting like the others, to mere touching of the tip, and finally to not 

 even this ; the hind toe is then said to be functionless. But the lowest 

 birds cannot stand upright on their toes at all ; these rest with the tarsus 

 horizontal, and the heel c touching the ground ; moreover, in all these birds, 

 the tail affords additional support, making a tripod with the legs, as in the 

 kangaroo. These birds might be called plantigrade, in strict anatomical 

 analogy with the beasts so called ; the others are digitigrade, quite as analo- 

 gously ; but there are no birds, that, like horses and cows, walk on the ends 

 of their toes, or toe-nails. A bird's ordinary walljing or running, corres- 

 ponds exactly with ours, as far as the mechanics of motion are concerned ; 

 but its hopping, as it is called, is really leaping, both legs being brought 

 forward at once. Nearly all birds down to GaUince, leap when on the 

 ground ; all others walk or run, advancing one leg after the other. Leaping 

 is thus really distinctive of the Insessores; though many of them, as tit- 

 larks, shore larks, meadow larks, many terrestrial sparrows, blackbirds, 

 crows, turkey buzzards, and others, including all the pigeon family, walk 

 instead of leajDing. 



§ 74. The Plumage of the legs varies within wide limits. In general, 

 the leg is feathered to the heel, and the tarsus and toes are naked. The 

 thigh is ALWAYS feathered. The cms is feathered in all Insessores (with 

 rare exceptions), and in all Natatores without exception; in the loon family 

 the feathering extends on as well as to the heel-joint. It is among the Cur- 

 sores, or walkers, and especially wading birds, that the crus is most naked ; 

 here it may be denuded half way up. A few waders — among ours, chiefly 

 in the snipe family — have the crus apparently clothed to the joint, but this 

 is in most if not all cases due to the length of the feathers, for probably no 

 one of them has the crural pteryla itself extended to the joint. The crural 



