120 GENERAL ORNITHOLOGY. 
xvnun, kneme, same as Lat. erws), which in some birds, as loons, runs high up in front above 
the knee-joint. Below, the tibia alone forms the ankle-joint, C, by srlioulntine with the next 
bone. For this purpose it ends in an enlarged trochiear (Gr. rpoxadia), or pulley-like surface, 
presenting a little forward as well as downward, above which, in many birds, there is a little 
bony bridge beneath which tendons passing to the foot are confined. This ttoishes the leg, 
consisting of thigh, A B, and leg proper, B C, bringing us to the ankle-joint at the heel, C. 
Now a bird’s legs, unlike outs, are not separate from the bedy 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 fect like hands, and least among the lowest swimmers. The range of variation, 
from greatest freedom to most extensive enelosure of the limb, is from a little above B nearly to 
C, as in the case of a loon, grebe, or penguin. In no bird is the kuec, B, seen outside the 
general contour of the plumage: it must be looked or felt for amoug 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 jott, 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 wrist of a horse’s fore-leg “knee.” People also eall a bird’s ervs or leg proper, B to (, 
the thigh,” and disregard the true thigh altogether. This coufusion 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. Anee is at junction of thigh and leg proper; 
it always bends forward; heel is at junction of leg with foot, and always bends backwavd. 
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, with 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 docs not usually come to 
table, having no flesh upon it. . (See frontispiece, Th, An, 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 (tig. 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 uo 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 boues, 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 hoad of the principal 
metatarsal bone, to be true tarsal elements, Morse went further, showing the tibial epiphysis, or uppor tarsal bone 
of Gegenbaur to be really two bones, which he held to correspond with tho tibialo and flbulare, or astragalus and 
calcaneum 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 80 characteristic of the tibia ot 
elves. The distal tarsal ossicle he believed to be the centrale of reptiles. Wyman discovered the so-called “ procoss of 
the astragalus” to have a distinct ossification, and Morse intorpretod it as tho infermedium of reptilos, Later 
views, however, as of Huxley and Parker, limit tho 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 abovo, 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 
. 
