54 $ A 1ST A 1 
cular cafes nutfl be different, and requires a very accurate 
examination of the circumftances both of the difeafe and 
patient. 
Though the true vertebrae agree in the general ftrufture 
above defcribed; yet, becaufe of feveral fpecialties proper 
to a particular number, they are commonly divided into 
th ree claffes, viz. cervical, dorjal, and lumbar . The cervical 
are the feven uppermoft vertebrae ; which are diftinguifh- 
ed from the reft by thefc marks: Their bodies are fmaller 
and more folid than any others; and flatted on the fore¬ 
part, to make way for the oefophagus; or rather this flat 
figure is owing to the p re flu re of that pipe, and to the ac¬ 
tion of the longi colli and anterior rem mufcles. They 
are alfo flat behind, where fmall proceflTes rife, to which 
the internal ligaments are fixed. The tranfverfe procelfes 
of thefe vertebra: are framed in a different manner from 
thofe of any other bones of the fpine. For, beiides the 
common tranverfe procefs rifing from between the oblique 
procelfes of each fide, there is a fecond one that comes out 
front the fide of the body of eaclt vertebra ; and thefe two 
procelfes, after leaving a circular hole for the paffage of 
the cervical artery and vein, unite, and are conliderably 
hollowed at their upper part, with rifing fides, to protect 
the nerves that pafs in the hollow; and at lalt each fide 
terminates in an obtufe point, for the infection of mufcles. 
The fpinal procelfes of thefe cervical bones hand nearly 
-firaight backwards, are fiiorter than thofe of any other 
vertebrae, and are forked or double at their ends; and 
hence allow' a more convenient infection to mufcles. 
, The cervical vertebrae have fome particular differences, 
which oblige 11s to confider them feparately. The firff, 
from its ufe of fupportingthe head, has the name of atlas-, 
.and is alfo called epijlrcphea, from the motion it performs 
on the fecond. The atlas, contrary to all the other ver¬ 
tebrae of the fpine, has no body; but, inftead of it, there 
is a bony arch. In the convex fore-part of' this arch a 
fmall rifing appears, where the mufeuli longi colli are in¬ 
fected ; and, on each fide of this protuberance, a fmall ca¬ 
vity may be obferved, w here the redli interni minores take 
their rife. The upper and lower parts are rough and un¬ 
equal, where the ligaments that conned! this vertebra to 
the os occipitls, and to the fecond vertebra, are fixed. 
The back-part of the arch is concave, fmooth, and cover¬ 
ed with a cartilage, in a recent fubjedt, to receive the 
tooth-like procefs of the fecond vertebra. 
The fuperior oblique procefs of this atlas are large, ob- 
-long, hollow, and more horizontal than in any other ver¬ 
tebra. They rife more in their external than internal 
brim; by which their articulations with the condyloid pro- 
ceffes of the os occipitis are firmer. Under the external 
edge of each of thefe oblique proceffes is the folia, or deep 
open channel, in which the vertebral arteries make the 
circular turn, as they are about to enter the great foramen 
of the occipital bone, and where the tenth pair of nerves 
go out. The inferior oblique proceffes, extending from 
within outwards and downwards, are large, concave, and 
circular. So that this vertebra, contrary to the other fix, 
receives the bones with which it is articulated, both above 
and below. 
The fecond vertebra colli is called dentata, from the 
tooth-like procefs on the upper part of its body. Some 
authors call it cpijlrophca ; but improperly, fince this defig- 
nation is only applicable to the firff, which moves on this 
its on an axis. The body of this vertebra is fomewhat of 
a pyramidal figure, being large, and produced downwards, 
efpecially at its fore-fide, to enter into a hollow of the 
vertebra below ; while the upper part has a fquare pro¬ 
cefs,-' with a fmall point Handing out from it. A ligament 
likewife goes out in an oblique-tranfverfe direction, from 
each fide of the procelfus dentatus, to be fixed at its o,her 
end to the firff vertebra, and to the occipital bone ; and 
.another ligament rifes up from near the point of the pro- 
cefs to the os occipitis. The fuperior oblique proceffes of 
■this vertebra are large, circular, very nearly in an horizon 
O M Y. 
tal pofition, and flightly convex, to be adapted to the in¬ 
ferior oblique proceffes of the firff vertebra. The inferior 
oblique proceffes of this vertebra anfwer exactly to the 
defeription given of thofe common to all the cervical ver¬ 
tebrae. 
The tranfverfe procelfes of the vertebra dentata are 
fhort, very little hollowed at their upper part, and not fork¬ 
ed at their ends; and the canals through which the cervi¬ 
cal arteries pafs are reflected outwards about the middle 
fubffance of each procefs; fo that the courfe of thefe vef- 
fels may be diredted towards the tranfverfe proceffes of the 
firff vertebra. Had this curvature of the arteries been 
made in a part fo moveable as the neck is, w hile they-were 
not defended by a bone, and fixed to that bone, fcarcely 
a motion could have been performed without the ut-moft 
hazard of compreflion, and a flop put to the courfe of the 
liquids, with all its train of bad confequences. Hence we 
obferve this fame mechanifm feveral times ufed, when 
there is occafion for a Hidden curvature of a large artery. 
The fpinal procefs of this vertebra dentata is thick, ftrong, 
and fhort, to give fufficient origin to the mufeuli redfi ma- 
jores and obliqui inferiores, and to prevent the contufion 
of thefe and other mufcles in pulling the head back. This 
fecond vertebra confifls, at the birth, of four bony pieces. 
For, befides the three already mentioned as common to all 
the vertebrae, the tooth-like procefs of this bone is bemm 
at this time to be oflified in its middle, and is joined as an 
appendix to the body of the bone. Left this appendix be 
bent or difplaced, good nurfes keep the heads of new-born 
children from falling too far backwards, by ftay-bands, or 
fome fuch means, till the mufcles attain ftrength fufficient 
to prevent that dangerous motion. 
The third vertebra of the neck is by fome called axis ; 
but this name is applied to it with much lefs reafon than 
to the fecond. This third, and the three below, have no¬ 
thing particular in their ftrudlure, but all their parts come 
under the general defeription formerly given, each of them 
being larger as they defeend. The feventh vertebra of the 
neck is near to the form of thofe of the back, having the 
upper and lower furfaces of its body lefs hollow than the 
others. The oblique proceftes are more perpendicular; 
neither fpinal nor tranfverfe procelfes are forked. This 
leventh and the fixth vertebra of the neck have the hole 
in each of their tranfverfe proceftes more frequently divided 
by a fmall crofs bridge, that goes between the cervical 
vein and artery, than any of the other vertebrae. 
The twelve dorfal may be diftinguiflied from the other 
vertebrae of the fpine by the following marks: Their bo¬ 
dies are of a middle fize, between thofe of the neck and 
loins ; they are more convex before than either of the other 
two forts; and are flatted laterally by the preflure of the 
ribs, which are infer ted into fmall cavities formed in their 
fides. This flatnefs of their fides, which makes the figure 
of thefe vertebras almoft an half oval, is of great ufe; as 
it affords a firm articulation to the ribs, allows the trachea 
arteria to divide at a fmall angle, and the other large vef- 
fels to run fecure from the adlion of the vital organs. Their 
bodies are more concave behind than any of the other two 
claffes. Their upper and lower furfaces are horizontal. 
The cartilages interpofed betw een the bodies of thefe ver¬ 
tebras are thinner than in any other of the true vertebra? 5 
and contribute to the concavity of the fpine in the thorax, 
by being thinneft at their fore-part. The oblique procef¬ 
fes are placed almoft perpendicularly; the upper ones flam¬ 
ing but a little forwards, and the lower ones ftanting as 
much backwards. Between the oblique proceftes of op- 
pofite fides, feveral fliarp [ recedes Hand out from the up¬ 
per and lower parts of the plates which join to form the 
fpinal proceftes ; into thefe, ftrong ligaments are fixed for 
connecting the vertebras. The tranfverfe proceftes of the 
dorfal vertebrae are long, thicker at their ends than in the 
middle, and turned obliquely backwards; which may be 
owirig to the preflure of the ribs, the tubercles of which 
are inferted into a depreffion near the end of thefjs procef- 
