COMPARATIVE ANATOMY. 
The lower end of the nlna is larger than 
that of the radios in the elephant ; but this 
eircumstance occurs in no otlier instance. 
The radius and ulna exist in the seal, 
manati, and whales, but in a flattened 
form. 
Several genera of mammalia possess a 
hand ; but it is much less complete, and 
consequently less useful than that of the 
human subject, which well deserves the 
name bestowed on it by Aristotle, of the 
organ of all organs. The great superiority 
of that most perfect instrument, the human 
hand, arises from the size and strength of 
the thumb, which can be brought into a 
state of opposition to the Angers, and is 
hence of the greatest use in grasping sphe- 
rical bodies, in taking up any object in the 
hand, in giving us a firm hold on whatever 
we seize; in short, in a thousand ofiices, 
which occur every moment of our lives, 
and which either could not be accomplish- 
ed at all, if the thumb were absent, or 
would require the concurrence of both 
hands, instead of being done by one only. 
Hence it has been justly described by 
Albinos as a second hand, “ manus parva 
major! adjutrix,” de sceleto, p. 465. 
All the slmice possess hands : but even in 
those, which may be most justly stiled an- 
thropomorphous, the thumb is small, short, 
and weak ; and the other fingers elongated 
and slender. In others, as some of the 
cercopitheci, there is no thumb, or at least 
it is concealed under the integuments ; but 
these animals have a kind of fore paw, 
which is of some use in seizing and carrying 
their food to the mouth, in climbing, &c. 
like that of the squirrel. The genus lemur 
has also a separate thumb. Other animals, 
which have fingers sufficiently long and 
moveable for seizing and grasping objects, 
are obliged, by the want of a separate 
thumb, to hold them by means of the two 
fore-paws ; as the squirrel, rat, opossum, 
&c. Those, which are moreover obliged to 
rest their body on the fore-feet, as the dog 
and cat, can only hold objects by fixing 
them between the paw and the ground. 
Lastly, such as have the fingers united by 
the integuments, or enclosed in hoofs, lose 
all power of prehension. 
The metacarpus is elongated in those ani- 
mals, where the toe only touches the ground 
in standing or walking ; and constitutes the 
part, which is commonly called the fore- 
leg ; as the carpus is termed the knee. 
The number of metacarpal bones is thp 
same with that of the fingers or fore-toes : 
except in the ruminating animals. Even in 
these there are two distinct metacarpal 
bones, lying close together before birth : 
the opposed surfaces first become thinner, 
then are perforated by several openings, 
and at last disappear ; so that the adult ani- 
mal has a single cannon bone, possessing a 
common medullary cavity internally, and 
marked on tlie outside with a slight groove 
at the place of the original separation. 
There is therefore but one metacarpal bone 
in the adult for the two toes. The struc- 
ture of the metatarsus is the same. 
The single finger or fore-toe of the horse 
is composed of the usual tlnee phalanges ; 
the first, which is articulated to the cannon, 
is called the pastern ; the 2d is the coro- 
net ; and the 3d the os basis or coffin bone ; 
on which the hoof rests. There are also 
two sesamoid bones at the back of the 
pastern joint ; and an additional part 
called the shuttle-bone connected to the 
coffin. 
In those animals, which have five toes, as 
the carnivora, &c. that which lies on the 
radial side of the extremity, and is there- 
fore analogous to the thumb, is parallel 
with the others ; and the animal conse- 
quently has not the power of grasping any 
object. The last phalanx in these supports 
the nail of the animal ; and sends a process 
into its cavity. These parts are so con- 
nected that the nail is naturally turned up- 
wards, and not towards the ground ; so that 
its point is not injured in the motions of the 
animal. The phalanx must be bent in 
order to point the nail forwards or down- 
wards. 
The order of rodentia have generally 
five toes : that which corresponds to the 
thumb being the shortest. 
The elephant has five complete toes ; 
but they are almost concealed by the thick 
skin. 
The pig has four toes ; two larger ones, 
which touch the ground ; and two smaller 
behind these, which do not reach so far. 
There is also a bone, which seems to be the 
rudiment of a thumb. 
The phalanges of the cetacea are flat- 
tened ; not moveable, and joined together 
in the fin. 
BONES OP THE BOWER EXTREMITY. 
The length of the femur depends on that 
of the metatarsus ; and it bears an inverse 
ratio to the length of that part. 
Hence it is very short in the horse, cow, 
&c. where the same mistakes are commonly 
