OSSEOUS SYSTEM. (Comp. Anat.) 
fin rays, however numerous, are connected ; 
with the exception of the first, which articulates 
immediately with the radius. In some Fishes, 
as in the Lophius, these bones are extraordi- 
narily Jengthened, while the radius and ulna 
are diminished in proportionate size; so that 
some writers have mistaken the bones of the 
ca a for those of the forearm. 
n the Batrachia, and in all four-footed Rep- 
tiles, they are small ossicles interposed between 
the bones of the forearm and metacarpal bones, 
resembling very much those of the human sub- 
ject; butin Birds, in consequence of the peculiar 
condition of the hand, here converted into a 
wing, they are reduced to two, so disposed as to 
form with the bones of the forearm a mere 
hinge-joint moving laterally, so as to allow the 
wing to be folded up. 
In the Cetacea the carpal bones exist, it is 
true, but so separated from each other by an in- 
terposed cartilaginous mass that they assist in 
_ forming a broad paddle, strengthened by super- 
ficial ligaments, and only useful for progression 
in the water. 
__Imall other Mammalia the carpal bones are 
met with, their form and number varying with 
_ the uses for which the limb of which they form 
a part is adapted. 
The metacarpal bones form the immediate 
basis on which the individual fingers are sup- 
ported, and, accordingly, are as variable in their 
number and arrangement as are the digital 
portions of the anterior extremity. 
In Fishes, owing to the numerous fingers or 
rays as they are here called, the metacarpal 
bones are met with in far greater numbers than 
in animals where the extremities assume a more 
concentrated form,—a fact most remarkably 
exemplified in the Chondropterygious Fishes, 
where the number of digital phalanges is enor- 
mous. But in Reptiles, where the hands are 
not only reduced to what may be called the 
normal type of structure, but developed in a 
medium condition, little remarkable is met 
_with in this part of the hand. It is only as we 
come to animals appointed to extraordinary 
conditions of life that aberrations from the 
usual form become conspicuous, as, for exam- 
_ ple, in the feathered races. The metacarpus of 
Birds, although in some cases it might at first 
appear composed of a single bone, in others of 
_ two bones anchylosed together at both ends, 
contains, in reality, the elements of three meta- 
_ carpal bones consolidated ; two of these, which 
are much elongated, supporting the fingers, 
while the third, an exceedingly small element 
confused with the base of the central one, sus- 
_ tains the rudimentary thumb. 
__In the metacarpal bones of the unguiculate 
- Quadrupeds there is nothing worthy of notice 
_ in this general survey of the osseous system ; but 
in the Ungulata a coalescence almost as re- 
_markable as in Birds is observable, whereby 
the peculiar structure of the feet of such animals 
is provided for. In the Ruminantia and So- 
idungula the whole metacarpal apparatus 
_ Would at first sight appear to consist of a single 
bone, to which the name of canon-bone is gene- 
ee 
841 
tally appropriated ; but this apparently single 
bone is easily seen to_be in reality made up of 
two, anchylosed together-throughout their whole 
length, so that the line of demarcation between 
them is only indicated by a deep longitudinal 
groove, visible on the anterior and posterior 
aspects of the bone; in most cases, however, 
there are two more lateral pieces, unattached to 
the principal or canon-bone except by the soft 
parts, but evidently real metacarpal elements in 
an imperfect and rudimentary condition. 
The digital phalanges being the most remote 
from the central portion of the skeleton are 
likewise the most variable in number and ap- 
pearance, being moulded into shapes as various 
as are the uses to which the anterior limbs are 
convertible, becoming in turn the framework of 
oars, of paddles, of pillars, of rakes, of wings, 
or of hands, in accordance with the different 
natures of the animals possessing them. Neither 
is it at all an easy task to say how many of 
these elements might exist in the construction 
of this part of the skeleton, seeing that the 
number of fingers that may enter into the com- 
position of a hand seems not at all determinate, 
nor even the number of phalanges in a given 
finger. The pectoral fins of osseous Fishes, the 
representatives of the hands of higherVertebrata, 
differ exceedingly in this respect, sometimes 
consisting of a single ray, at others being dilated 
and extended, as in the Flying Fishes, until both 
rays and phalanges become extremely numerous. 
The hand or pectoral fin of the Skates is per- 
haps one of the most remarkable structures 
that can he offered to the contemplation of the 
osteologist, whether we regard its apparently 
disproportionate size or the immense number 
of digital elements that enter into its composi- 
tion ; it forms, in fact, the great bulk of their 
bodies, and is made up of upwards of a hundred 
distinct fingers, each composed of numerous 
phalanges ofenormous length. Throughout the 
Serpent tribes all traces of, anterior extremities 
are lost, but in the Anourous Batrachia fingers 
again appear under a new and more elevated 
form, although feeble when compared to the 
digital phalanges of the hinder extremities in 
the same Reptiles. 
Throughout the Saurian and Chelonian races 
as they now exist, nothing remarkable appears 
in the construction of this portion of the skele- 
ton, the chief modifications observable being in 
the number, length, and position of the fingers, | 
although in extinct forms of nearly allied genera, 
such as the Ichthyosaurus and Plesiosaurus, 
the number both of toes and phalanges are so 
prodigiously increased that we are once more 
reminded of the fins of Fishes, 
The digital phalanges in the wing of a bird 
are reduced to an exceedingly rudimentary 
condition, the thumb being represented by a 
single bone. The central or radial finger is the 
longest and most complete, consisting, when 
fully developed, of three distinct joints, though 
sometimes there are only two. The ulnar or 
third finger is, like the thumb, represented by a 
single phalanx appended to the distal extremity 
of the ulnar metacarpal bone. 
