120 GENERAL OBNITHOLOGY. 



Kvrjfit], Jcneme, same as Lat. cms), which iu some birds, as loons, runs high up in front above 

 tlu' kueo-joint. Below, the tibia alone forms the ankle-joint, C, by articulating with the next 

 bone. For this purpose it ends in an enlarged trochlear (6r. TpoxaXia), or pulley-like surface, 

 presenting a little forward as well as downward, above which, in numy birds, there is a little 

 bony bridge beneath which tendons passing to the foot are confined. This finishes the leg, 

 cfmsisting of thigh, A B, and leg proper, B C, bringing us to the ankle-joint at the heel, C. 



Now a bii-d's legs, unlike ours, are not separate from the body from the hip downward ; 

 but, for a variable distance, are enclosed within the general integument of the body. The 

 freedom of the limb is greatest among the high perching birds, and especially the Raptores, 

 which use the feet like hands, and least among the lowest swimmers. The range of variation, 

 from greatest freedom to most extensive enclosure of the limb, is from a little above B nearly to 

 C, as iu the case of a loon, grebe, or penguin. In no bird is the knee, B, seen outside the 

 general contour of the plumage : it must be looked or felt for among the feathers, and in most 

 prepared skins will not be found at all, the femur having been removed. It is a point of little 

 practical consequence, though hearing upon the generalization just made. The first joint, or 

 bending of the limb, that appears beyond a bird's plumage is the heel, C ; and this is what, 

 in loose popular parlance, is called " knee," upon the same erroneous notions that make people 

 call the wi'ist of a horse's fore-leg '' knee." People also call a bird's C7'us or leg proper, B to C, 

 the ''thigh," and disregard the true thigh altogether. This confusion is inexcusable; any one, 

 even without the slightest anatomical knowledge, can tell knee from heel at a glance, whatever 

 their respective positions relative to the body. Knee is at junction of thigh and leg proper ; 

 it always bends forward; ZteeHs at junction of leg with foot, and always bends backward. 

 This is as true of a bird, which is digitigrade, that is, walks on its toes with its heels in the 

 air, as it is of a man, who is plantigrade, that is, walks on the whole sole of the foot, vrith the 

 heel down to the ground. In a carver's language, the thigh is the "second joint" (from 

 below) ; the leg is the "drumstick " ; the rest of a fowl's hind limb does not usually come to 

 table, having no flesh upon it. (See frontispiece, Th, Kn, Lg.) 



Before proceeding to the next segment of the limb, I must dwell upon the ankle-joint, 

 situated at the heel, — the point C, — corresponding to the carpal angle or bend of the wing, 

 C in fig. 27. There we found, in adult birds, two small carpal bones, or bones of the wrist 

 proper; and noted the presence in the embryo of several other carpals (fig. 29), which early 

 fuse with the metacarpus. Just so in the ankle, there are in embryonic life several tarsal bones, 

 or bones of the tarsus (Lat. tarsus, the ankle) ; all of which, however, soon disappear, so that 

 there appears to be no tarsus, or collection of little bones between the tibia and the next 

 segment of the limb, the metatarsus. An upper tarsal bone, or series of tarsal bones, fuses 

 with, the lower end of the tibia, making this leg-bone really a tibio-tarsus ; and similarly, a 

 lower bone or set of bones fuses with the upper end of the metatarsus, making this bone a 

 tarso-metatarsus. So there are left no free bones in the ankle-joint, which thus appears to be 

 immediately between the leg-bone and the principal foot-bone; but which is nevertheless 

 really between two series of tarsal bones, the identity of which has been lost.^ 



1 The exact homologues of a bird's vanishing tarsal bones are still questioned. Gegenbaur showed the so- 

 called epiphysis or shoe of bone at the foot of the tibia, and the similar cap of bone on the head of tlie principal 

 metatarsal bone, to be true tarsal elements. Morse went further, showing the tibial epiphysis, or upper tarsal bone 

 of Gegenbaur to be really two bones, which he held to correspond with the tibiale and flbulare, or astragalus and 

 ca?ca?ieMm of mammals; these subsequently combining to form the single upper tarsal bone of Gegenbaur, and 

 finally becoming anchylosed with the tibia to form the bitrochlear condylar surface so characteristic of the tibia ot 

 Aves. The distal tarsal ossicle he believed to be the centrale of reptiles. Wyman discovered the so-called " process ot 

 the astragalus " to have a distinct ossification, and Morse interpreted it as the intermedium of reptiles. Later 

 views, however, as of Huxley and Parker, limit the tibial epiphysis to the astragalus alone of mammals. If these 

 opinions be correct, other tarsal elements (more than one) are to be looked for in the epiphysis of the metatarsus. 

 Whatever the final determination of these obscure points may be, it is certain that, as said in the text above, the 

 lower end of a bird's tibia and the upper end of a bird's metatarsus include true tarsal elements, just as the upper 



