ANATOMY. 
The teeth . — These organs are composed 
internally of a very hard bony substance ; 
and are covered externally by a still harder 
matter, called the cortex or enamel. — 
Each tooth has a body or crown, which is 
the part seen in the mouth ; a neck, round 
which the gum adheres ; and one or more 
fangs or roots, which are sunk in a process 
of the jaw, called the alveolar. These bo- 
dies are not formed in a nidus of cartilage, 
like bones, but on a soft vascular body, 
called a pulp, which may be compared to 
the core, on which a horn is formed. This 
is surrounded by a delicate membrane called 
the capsule of the tooth. When the teeth 
are being formed, these pulps and capsules 
with the rudiments of the teeth, are lodged 
in cavities hollowed out of the jaw-bone. 
They afterwards rise, and, piercing the gum, 
appear in the mouth. 
Teeth differ from other bones in possess- 
ing no vessels nor nerves in their substance. 
As they are destined for the merely mecha- 
nical function of triturating the food, such 
parts would not have been suitable to this 
office. The pain of tooth-ach arises from 
a nerve, which, with a vessel, resides in a 
hollow, formed in the centre of the fang and 
body of each tooth. These parts are ex- 
posed by the decay. The teeth, in conse- 
quence of possessing no vessels, are only 
affected by chemical and mechanical causes. 
They do not repair the effects of trituration, 
nor of accidental injury ; nor do they suffer 
from any of the diseases, which affect other 
bones. 
There are two sets of teeth ; the first are 
fewer in number, and smaller in size ; as they 
fall out at a certain age, to make room for 
other larger ones, they are called deciduous 
or temporary. The second set lasts through- 
out life, and are called the adult or perma- 
nent set. 
The latter consists of 32 teeth; 16 in 
each jaw. There are four incisores or cut- 
ting teeth in front ; 2 canini or cuspidati, or 
dog teeth, placed one on each side of the for- 
mer ; 4 bicuspides behind the last ; and 6 mo- 
lares behind these. From the late period at 
which the last molaris appears, it is called 
the dens sapientiae, or wise tooth. 
The temporary set consists of twenty 
teeth; ten in each jaw. There are 4 in- 
cisores ; 2 cuspidati ; and 4 molares. 
The permanent teeth are lodged at first 
in cavities of the jaw, near the roots of the 
temporary ones ; and as these last are shed, 
rise up to supply their places. 
The bone of the tongue is called os 
hyoides from its very accurate resemblance 
to the Greek u. It consists of a body, two 
cornua, and two appendices, which are in 
fact so many separate bits of bone. 
The bones of the trunk consist of those of 
the spine, thorax, and pelvis. 
The spine consists of twenty-four true or 
moveable vertebra; an os sacrum, and an 
os coccygis (which indeed is composed of 
four pieces): these last bones bearing con- 
siderable resemblance to the vertebra, are 
called sometimes the false vertebras. 
Each vertebra has a body, which is situ- 
ated anteriorly, and consists of a cylindrical 
piece of bone; a perforation behind tiiis, in 
which the spinal morrow runs ; two superior 
and two inferior articulating processes, by 
whicii it is joined to the bone immediately 
above and below' it; two transverse pro- 
cesses, and one spinous process, which pro- 
jecting behind, forms a sharp ridge, from 
which the name of spine has been applied 
to the whole column. 
The vertebraj are divided into three clas- 
ses, according to their situation : the seven 
upper ones are called cervical : of these, the 
first, that immediately supports the head, is 
called the atlas ; and the second, from a re- 
markable bony process which it possesses, 
the vertebra dentata. The twelve next are 
called dorsal vertebras, and are distinguished 
by having the ribs articulated to them. The 
five last are called lumbar. These all differ 
from each other in some circumstances. 
The most obvious distinction arises from the 
size : the upper ones are the smallest, and 
there is a gradual increase as we descend. 
The column of the spine, when viewed 
altogether, is not perpendicular; it stands 
forwards in the neck, recedes in the upper 
part of the back, and projects again in the 
loins. Holes are left between the bones for 
the transmission of the nerves which arise 
from the spinal marrow. 
The sacrum forms the back of the pelvis, 
and is hollowed out in front. In form it is 
triangular, and the base is joined to the last 
vertebra. It is perforated by a canal, in 
which the termination of the medulla spinalis 
is lodged. Its apex has connected to it the 
os coccygis. 
The thorax is formed by the twelve dor- 
sal vertebrae, the ribs, and sternum. The 
ribs are long, curved, flattened, and narrow 
bones, attached behind to the dorsal verte- 
brae both in their bodies and transverse 
processes, and joined in front to a piece of 
cartilage. They are twelve in number, and 
the seven upper ones, whose cartilages are 
affixed to the sides of the sternum, are called 
true ribs; the live lower ones, the cartilages 
