844 
toes are more or less numerous. In_ their 
most normal state of developement these bones 
are five in number as in the human skeleton, 
but from this variations occur in almost every 
order of Vertebrata. 
The metatarsus of Reptiles is, however, well 
developed, consisting of a series of moderately 
elongated bones extended between the carpus 
and the proximal phalanx of the corresponding 
toe, but offering nothing worthy of special 
comment. 
The tarso-metatarsal bone of Birds, repre- 
senting both the tarsal and metatarsal portions 
of the skeleton, seems to consist of three and 
sometimes four metatarsal bones consolidated 
into one piece. These are distinguishable in- 
feriorly by the four trochlear surfaces that sup- 
port the moveable toes ; while the presence of 
an ossified spur in some gallinaceous birds, 
regarded by many anatomists as the rudiment 
of a fifth toe, might indicate the existence of a 
fifth metatarsal element lost in the general 
consolidation of these pieces. 
In all the unguiculate Mammals the meta- 
tarsal bones hold the same relations with the 
other bones of the foot as in the skeleton of 
Man, and need no special notice; but in the 
Ungulate families their appearance and arrange- 
ment are necessarily much changed. In the 
Solipeds and Ruminants the metatarsal division 
of the extremity is so much elongated as to 
constitute a very considerable portion of the 
limb. It is principally made up of a single 
piece generally called the “canon bone,” 
which in reality consists of two enormous meta- 
tarsal bones consolidated into one, being fused 
together in the central line along their whole 
length, although the real composition of the 
canon bone is always distinguishable both on 
account of a deep furrow which indicates the 
union of the two pieces, and from the con- 
dition of the two widely separated trochlear 
surfaces at its distal extremity. Besides the 
two largely developed pieces forming the canon 
bone, two other metatarsal pieces assist in form- 
ing the foot of a Ruminating Quadruped ; these 
sustain the supplementary toes developed in a 
rudimental condition on the outer and inner 
aspects of the member. — 
The digital phulanges of the posterior ex- 
tremity are among the most variable elements 
of the skeleton, being, like those of the anterior, 
made subservient to a great variety of uses both 
in terrestrial and aquatic forms of Vertebrata. 
In the osseous Fishes they are represented 
by the fine rays of the ventral fin, and are of 
course employed in natation ; but in the carti- 
laginous Fishes, as the Sharks and Rays, 
although the resemblance between this part of 
the skeleton and the feet of higher animals is 
more striking than in the gsseous races, they 
are appropriated to a different office, serving 
the purpose of claspers, whereby the intercourse 
between the sexes is facilitated. 
Throughout all the Reptilia that possess 
hind feet, the phalanges of the toes offer 
nothing remarkable; neither in Birds is there 
anything peculiar in their structure, the only 
circumstances of interest connected with this 
OSSEOUS SYSTEM. (Comp. Anat.) 
part of the skeleton in the feathered races _ 
relating to the number and disposition of the — 
toes, and the presence of more or less numerous 
joints entering into their composition. =. 
In the Mammalia this part of the foot cor- 
responds in its composition with that of the 
hand, and therefore need not be further noticed. 
In enumerating the elements of the endo- 
skeleton it would be — to omit certain 
supplementary pieces, which, though not strie 
belonging to the osseous system, are of important 
mechanical assistance to the muscles inserte 
into different portions of the skeleton. 
are alone: in the substance of 
tendons where much friction is encountered, : 
where it is of importance to remove the line ¢ 
traction to some distance from the centi 
motion in order to gain additional 
When developed in the tendons of the finger 
or toes, these detached pieces of osseous sul 
stance are called ‘ sesamoid bones,” but i 
such situations their existence is by no meat 
constant. Connected with the great joi 
corresponding with the knee and elbow of t 
human subject, bones of this kind are ¥ 
generally developed, and their size and ij 
portance renders them worthy of special remai 
In the anterior extremity the superadded bo 
are named “ olecranon,” and very generally | 
found solidly cemented to the proximal end 
the ulna, forming a prominent process, thatgi 
great mechanical advantage to the exte 
muscles of the forearm. The correspon¢ 
bone appended to the knee-joint has, from 
condition in the human subject, received 
name of “ patella.” a 
Such being the elements employed 
nature in constructing the locomotive e% 
mities of Vertebrate animals, our only 4 
der is that by simply modifying the 
of the bones, by suppressing some — 
exaggerating others, or else by fusing sev 
of them together, such infinite diversity 
apparatus is provided in the various 
ertebrata. Seldom, indeed, does a 
present all the pieces we have enumerated 
complete state of developement, and freqt 
the majority of them, or even the whole 
is entirely dispensed with. In many F 
as in the Lamprey and Myxine, all fot 
tremities are absolutely wanting, a circum 
which again becomes remarkable in the ¢ 
Ophidian Reptiles. Occasionally 
only are called into existence, and that 
very rudimentary state, as for example, it 
Serpents, Anguis, Boa, &c. More fre 
the anterior limbs are found without t 
terior ; such is the case in the apodal Fy 
the Siren and Bimanes among a 
still more conspicuously in the Cetacea 
ExoskeLeTon.—Having thus exam 
the elements that belong properly to the 
system or endo-skeleton, we must 
our attention to another important sy 
organs equally concerned in building 
framework of the body, and. that to an 
which the human osteologist would | 
imagine possible. We allude to the 
or cuticular skeleton, which, although fF 
