EXTERNAL PARTS OF BIRDS.—THE FEET. Apal 
The next segment of the limb. C to D. or the foot proper. is represented by the principal 
wietatarsal bone, mi. This corresponds te the human tastep or arch of the foot. nearly from 
the aukle-joint quite te the roots of the toes. The metatarsal bone, like the metacarpal of 
the hand, which it represents in the foot. is a compound one. Besides including the evanes- 
cent tarsal element or elements already specified. it consists of three metatarsal bones con- 
solidated In one, just as the metacarpal is tripartite. Among recent birds, the three are 
partly distinet only in the penguins: but in all, excepting ostriches. the origival distinction is 
indicated by three prongs or stumps at the lower end of the bone, forming as many articular 
surfaces for the three anterior tocs. The other toe most birds possess. the hind toe. is hinged 
upen the metatarsns in a different way. by means of a small separate metatarsal bone. quite 
imperfect: this is the aevessery metatarsal, am. It is situated near the lower end teward the 
Mnuer side of “he principal metatarsal bone. and is of various shapes and sizes: it has no true 
jeivting with the latter, but is simply pressed elose upon it. much as the fibula is applied to the 
dbin, or partly seldered with it. Above. it is defective: below, it bears a good meet for artien- 
lation with the hiad tee. ES" In spite of anatomical proprieties, the metatarsal part of a bird's 
ft — from heel to base of toes — from C to D. ‘s in ordinary deseriptive ornithelugy tneartably 
ealled “* The Tas. +s": a wreng name, but one so firmly established that it would be finical 
and futile te attempt to ‘substitute the correc: name. In the ordinary attitude of most birds. 
it is held more or less upright. and seems t+ be rather “leg” than a part of the * foot.” It is 
vulgarly called * the shank.” These points must br ingrained in the student's mind to 
prevent confusion. (See fig. 112 bis. p. 229.) : 
The divfis of the foot. or fees. upon which alone mes: birds walk or perch. consist of 
cerain numbers of small bones placed end to end, all joiuted upen one another, and the basal 
or proximate ones of each toe separately jointed either with the principal or the accessory meta- 
tarsal bone. Like those of the fingers. these bones are called phalanacs (Lat. phalanr. a 
rank or series) or inferncdes (because coming between any two joints or nodes of the toes). 
The furthermeost one of each almost invariably bears a nail or claw (tnguis . The phalanges 
are of various relative lengths. and of a variable number in the same cr different tees. But all 
these points. being matters of deseriptive ornithology rather than of anatomy proper, are fully 
reated beyond. as is also the special horny or leathery covering of the feet usually existing 
fom the point C outwani. We may here glance at the 
Mechanism of these Bones. — The hip is a ball-and-socket joint, permitting round-about 
es Well as fore-ani-att movements of the whole limb. though more restricted than the shoulder- 
joint. The knee is usually a strict ginglymus (Gr. ytyyAupos. gigglumas, binge) or binge-joint. 
allowing only backward and forward motion: and so constructed thai The forward movement of 
the leg is never carried beyond a right line with the femur, while the backward is se extensive 
that the lez may be gute doubled under the thigh. In some birds there is a slight nvtatery 
motion a: the knee. very evident in certain swimmers. by which the foot is thrown outward, so 
that the broad webbed toes may net “interfere.” The heel or ankle-juint is a strict hinge: its 
bendiz.gs are just the reverse of these of the knee: for the foot cannot pass back of a right line 
with the leg. but can come forward till the ices nearly touch the front uf the knee. In some 
~ binds the details of structure are such that. with the assistance of certain muscles. the foot is lacked 
mpen The leg when completely straightened out. so firmly that some little muscular effert is re- 
quired to overcome the obstacle: birds with this arranzement sleep securely standizg on one leg. 
which is the design of the mechanisr. The jointing of the toes with the prengs of the meta- 
tarsus is peculiar: for the articular surfaces are so disposed in a certain oblicuity. that when 
end of the metacarpus includes carpal elements: and thar 4 birnd’s anklejoint is set tihio-tarsal or between 
leg-bone and fsoc-bores. as in mammals, but between proximal and distal series cf tarsal bones. and sherefore. 
medio-tarsal. is in reptiles. 
