554 A N A T O M Y. 
furfdee, where the pronator radii teres is fixed. The body 
of the radius is convex on its internal and pofterior fur- 
faces; but the furfaces next to the ulna are flatted and. 
rough, for the origin of the mufcles of the hand ; and 
both terminate in a common fharp fpine, to which the 
ffrong ligament extended between the two bones of the 
fore-arm is fixed. The lower end of the radius is larger 
than the fuperior ; its back-part-has a flat ftrong ridge in 
the middle, and foflae on each fide. In a final! groove, 
immediately on the .outfide of the ridge, the tendon of the 
extender vertii mternodii pollicis plays. In a large one be¬ 
yond tliis, the tendons of the indicator and of the common 
extenfor mufcles of the finger's pafs. Contiguous to the 
ulna there is a fmall depreflib'n made by the extenfor mi¬ 
nimi digiti. On the infide of the lidge there is a broad 
deprefiion, which feems again fubdivided, where the two 
tendons of the bicornis, or extenfor carpi radial is, are 
lodged. The internal fide of this end of the radius is alfo 
hollowed by the extenfors of the firft and feco'nd joint of 
the thumb ; immediately above -which a little rough fur- 
face fliews where the fupinator radii longus is inferred. 
The ridges at the Tides of the grooves, in which the ten¬ 
dons play, have an annular ligament fixed to them, by 
which the feveral- (heaths for the tendons are formed. 
The fore-part of this end of the radius is alfo deprefied, 
where the flexors of the fingers and flexor carpi radialis 
pafs.. The external fide is formed into a femilunated 
fmooth cavity, lined wdth a cartilage, for receiving the 
lower er.d of the ulna. The lowed part of the radius is 
formed into an oblong cavity.; in the middle of which is a 
fmall tranfverfe riling, gently hollowed fer lodging muci¬ 
laginous glands; w hile the rifing itfelf is inlinuated into 
the conjunction of the two bones of the wrift that are re¬ 
ceived into the cavity. The internal fideof this articula¬ 
tion is fenced by a remarkable procefs of the radius, from 
-which a ligament going out to the wrift, as the ftyloid pro- 
cefs of the ulna with its ligament, guard it on the outfide. 
As the head of the radius receives the tubercle of the os 
humeri, it is not only bended and extended along with the 
■ulna, but may be moved round its axis in any pofition ; 
and, that this motion may be■ fufficiently large, the liga¬ 
ment of the articulation is extended, further down than 
ordinary, on the neck'of this bone, before it is conneCled 
to it; and it is very thin at its upper and lower part, but 
makes a firm ring- in the middle. This'bone is alfo joined 
to the ulna by a double articulation. When the palm is 
turned uppermoft, the radius is faid to perform the fupi- 
natioh : when the back of the hand is above, it i-s faid to 
be prone. But then the quicknefs and large extent of >hefe 
two motions are aflifted by the ulna, which can move with 
a kind of fmall rotation on the (loping Tides of the pulley. 
This lateral motion, though very inconflderable in the 
joint itfelf, is confpicuous at the lower end of fuch a long 
bone; and the ftrong ligament connecting this lower end 
to the carpus, makes the hand more readily obey thefe 
motions. When we defign a large circular turn of the 
hand, we increafe it by the rotation of the os humeri, and 
fometimes employ the fpine and inferior extremities, to 
make thefe motions of pronation or fupination of the hand 
large enough. 
The hand comprehends all from the joint of the wrift to 
the points of the fingers. Its back-part is convex, for 
greater nrmnefs and ftrength ; and it is concave before, 
for containing more furely.and conveniently fuch bodies 
as we take hold of. One-half of the hand has an obfeure 
motion in comparifon of what the other has, and ferves 
as a bafe to the moveable half; which can be extended 
back very little farther than to a ftraight line with the 
fore-arm, but can be confiderabiy bent forwards. As the 
bones that conipofe the hand are of different (hapes and 
ufes, while feveral of them that are contiguous agree in 
fomc general characters ; the hand is, on this account, 
commonly divided into carpus, metacarpus, and fingers ; 
among which laft the thumb is reckoned. 
The carpus is corcpofed of eight fiball fpongy bones, 
viz. os fcaphoides, lunare, cuneiforme, pififorme, trape¬ 
zium, trapezoides, magnum, unciforme. Os fcaphoides is 
convex above, concave-'and oblong below; from which 
fmall refemblance to a boat it has its name. I>:s fmooth 
convex furface is"divided by a rough middle forth, which 
nins obliquely-acrofs it. liie upper largeft divifion is ar¬ 
ticulated with the radius. The common ligament of the 
joint of the wrift is fixed into the folia; and the lower 
divifion is joined to the trapezium and trapezoides. The 
concavity receives more than an half of the round head of 
the os magnum. The external fide of this hollow is formed 
into a femilunar plane, to be articulated with the following 
bore. Os lunare has a fmooth convex.upper furface, by 
which it is articulated with the radius. The internal (ide, 
which gives name to the bone, is in the form of a crefcenf, 
and is joined with the fcaphoid ; the lower furface is hol¬ 
low, for receiving part of the head of the os magnum. On 
the outfide of this cavity is'another fmooth, but narrow, 
oblong (inuofity, for receiving the upper end of the os un¬ 
ciforme ; on the outfide of which a fmall convexity is 
found, for its connexion with the os cuneiforme. Between 
the great convexity above, and the firft deep inferior ca¬ 
vity, there is a rough fofik, in which the circular ligament 
of the joint ot the wrift.is fixed. Os cuneiforme is broader 
above, and towards the back of the hand, than it is below 
and forwards ; which gives it the refemblance of a wedge. 
The fuperior (lightly convex furface is included in the joint, 
of the wrift, being oppofed to the lower end of the ulna. 
Below this the cuneiform hone has a rough fofla, wherein 
the ligament of the articulation of the wrift is fixed. Os 
pifforme is almoft (pherical, except one circular plane or 
(lightly hollthv furface, which is covered with cartilage for 
its'motion on the cuneiform -bone, from which its whole 
rough body is-prominent forwards into'-the palm ; having 
the tendon of the flexor carpi ulnaris, and a ligament from 
the ftyloid procefs of the ulna, fixed to its upper part; the 
tranfverfe ligament of the wrift is conneCTedto its internal 
(ide; ligaments extended to the unciform bone, and to the 
os metacarpi of the little finger, are attached to its lower 
part; the abdudfer minimi digiti has its origin from its 
fore-part; and, at the internal fide of it, a fmall deprefiion 
is formed, for the partage of the ulnar nerve. Trapezium 
has four unequal Tides and'angles* in its back-part, from 
which it has its name. Above, its furface is fmooth, 
(lightly hollowed, and Temicircular, for its conjunftion 
with the os fcaphoides.- Its external (ide is an oblong con¬ 
cave fquare, for receiving the following bone. The infe¬ 
rior furface is formed into.a pulley ; the two protuberant 
(ides of which are external and internal. On this pulley 
the firft bone of the thumb is moved. Os trapezoides, fo 
called from the irregular quadrangular figure of its back- 
part, is the fmalleftbone of the wrift except the pififorme. 
The figure of it is an irregular cube. It has a fmall hol¬ 
low furface above, by which it joins 'he fcaphoides; a long 
convex one internally, where it is contiguous to the trape¬ 
zium; a fmall external one, for its conjunction with the 
os magnum; and an inferior convex furface, the edges of 
which are, however, fo raifed before and behind, that a 
fort of pulley is formed, where it Curtains the os metacarpi 
indicis. Os magnum, fo called becaufe it is the largeft bone 
of tlie carpus, is oblong, having four quadrangular (ides, 
with a round upper end, and a triangular plain one below. 
The round head is divided by a fmall riling, oppofite to 
the connection of the os fcaphoides and lunare, which to¬ 
gether form the cavity for receiving it. On the infide a 
(hort plain furface joins the os magnum to the trapezoides. 
Os unciforme has its name from a thin broad procefs that 
(lands out from it forwards into the palin, and is hollow 
on its infide, for affording paffag.e to the tendons of the 
flexors of the fingers. To this procefs alfo the tranfverfe 
ligament is fixed that binds down and defends thefe ten¬ 
dons; and the flexor and abduCtor mufcles of the little fin¬ 
ger have part of their origin from it. The upper plain 
furface is fmall, convex, and joined with the os lunare; 
the internal fide is long, and (lightly convex, adapted to 
a ' the 
