CHAPTER I. 
Sutura tranfverfalis (Tab. iii. iv.) runs acrofs the face, through the bot- 
toms of the orbits of the eyes; it joyns the lower edge of the frontal bone 
to the os fphcnoidcs, maxillas fuperioris, ofla nail, ungues, plana, palati, 
and jugalia, or malarum. 
The icull being divided into many bones, is neither fo fubje£t to fra¬ 
ctures, nor to have fractures fo far extended, as it would have been were 
it compofed of one bone only. This ftru&ure is alfo convenient for the 
offification of the bones, as has been already fhewn, and for the birth; 
bccaufe thefe bones not being perfect at that time, may be preffed toge¬ 
ther and make the head lefs. 
Ten of the bones of the head compofe the cranium, to contain the 
brain and defend it from external injuries. 
Ofia parietalia or bregmatis (Tab.iv. vi. vii.) are two large bones which 
compofe the fuperior and lateral parts of the icull; on the inlide they are 
remarkably imprinted by the arteries of the dura mater. 
Os fronds (Tab. iii. iv. vii.) makes the upper and forepart of the era* 
nium; its lower parts compofe the upper parts of the orbits of the eyes, 
where on its infides are impreffed the volvuli of the brain, which un- 
evennefles help to keep that part of the brain fteddy; in its middle above 
the os ethmoides ufually arifes a thin fpine, which ffrengthens that part 
of the bone, it being otherwife weak from its flatneis. In fome fculls this 
fpine is wanting; but then the bone is ufually thicker in that place, and 
from its middle, externally, goes a proccfs which fupports the bones of 
the nofe. Immediately above the os ethmoides in this bone is a fmall 
blind hole, through which runs a vein into the beginning of the longitu¬ 
dinal finus of the dura mater; and on the upper edge of each orbit, a fmall 
perforation, or a notch, through which nerves and an artery pafs fecure 
to the forehead; it has alfo a fmall hole in each orbit near the os planum, 
through which palfes a branch of the fifth pair of nerves. In the fubftance 
of this bone near the nofe are two, three, four, and fometimes five fi- 
nufes, which open into the nofe; (Tab. vii.) they differ very much in dif¬ 
ferent perfons, and arc very rarely found in children. Thefe finufes, and 
the fpine in this bone, make it very dangerous, if not impracticable, to 
apply a trephine on the middle and lower part of the forehead. 
Os ethmoides or cribriforme (Tab. vii. viii.) is a fmall bone about two 
inches in circumference, fcated in the anterior part of the bafis of the fcull, 
being almofl lurrounded by the laft delcribed bone; it is full of holes like 
a fieve, through which it is laid the olfaCtory nerves pafs, which I could 
never difeover. In its middle arifes a large procefs named chrifta galli: 
