A N A 1 
the contiguous os magnum. The external furface is ob¬ 
lique, and irregularly convex, to be articulated with the 
cuneiform bone. The lower end is dividedlnto two con¬ 
cave furfaces; the external is joined with the metacarpal 
bone of the little.finger, and tile internal one is fitted to 
the metacarpal bone of the ring finger. 
The three firfi bones of the carpus make an oblong head, 
by which they are articulated with the cavity at the lower 
ends of the bones of the fore-arm, fo as to allow' motion 
on all fides; and, by a quick fucceffioti of thefe motions, 
they may be moved in a circle. But as the joint is pblong, 
and therefore the two dimenfions are unequal, no motion 
is allowed to the carpus round its axis, except what it has 
in the pronation and fupination along with the radius. -The 
articulation of the firft three bones of the fuperior row, 
with th.e bones of the inferior, is fitch as allows of motion, 
efpecialiy backwards and forwards ; to the fecurity and 
ealinefs of which, the reception of the os magnum into the 
cavity formed by the -fcaphoides and lunare confiderably 
contributes; and the greatefl number of the mufcles that 
1 'erve for the motion of the wrifi: on the radius, being 
inferted beyond the conjunction of the firfi: row of bones 
with the fecond, a£t equally on this articulation as they do 
on the former; but the joint formed with the radius being 
the nioft ealily moved, the firfi effelt of thefe mufcles is on 
it, and the fecond row of the carpus is only moved after¬ 
wards. On account of the many tendons that pals upon 
the lower end of the fore-arm and the carpus, and of the 
numerous ligaments of thefe tendons and of the bones, 
which have lubricating liquors fupplied to them, the pain 
of fprains here is acute, the parts take a long rime to re¬ 
cover their tone, and their'fwellings are very obftinate. 
The metacarpus confifis of four bones which fuftain the 
fingers. Each bone is long and round, with its ends larger 
than its body. The upper end, which fome call the bale, 
is flat and oblong, without any confiderable head or cavity ; 
but it is fomewhat hollowed, for the articulation with the 
c.arpus; it is made flat and fmooth on the fides where thefe 
bones are contiguous to each other. Their bodies are flat¬ 
ted on their back-part by the tendons of the extenfors of 
the fingers. The lower ends are raifed into large oblong 
fmooth heads, whofe greatefl extent- is forwards front the 
axis of the bone. At the fore-part of each fide of the root 
of each of thele heads, one or two tubercles (land out,, for 
. fixing the ligaments that go from one metacarpal bone to 
another, to preferve them from being drawn afundetv. 
round the heads.a rough ring may be remarked, for the 
capfuiar ligaments of the firfi joints of the fingers to be 
fixed to ; and both fides of thefe heads are flat, by prefling- 
on each other. The metacarpal bones are joined above 
to the offa carpi, and to each other by nearly plain fur- 
faces ; and they may be diftinguifiled from each other'by 
the following marks : the os metacarpi indicis is generally 
the longeft. Its bafe, which is articulated with the os 
trapezoides, is hollow in the middle. The fmali ridge on 
the internal fide is fmaller than the one oppofite to it, and 
is made flat on the fide by the trapezium. The exterior 
ridge is alfo fmooth, and flat on its outfide, for its con¬ 
junction with the os magnum ; immediately below which 
a femicircular fmooth flat furface (hews the articulation of 
this to the fecond metacarpal bone. The back-part of this 
bafe is flatted where the long head of the extenfor carpi 
radialis is inferted, and its fore-part is prominent where 
the tendon of the flexor carpi radialis is fixed. Os meta- 
carpi medii digiti is generally the fecond in length, but of¬ 
ten it is as long as the former; fometimes it is longer, and 
it frequently appears only to equal the firfi by the o-s mag¬ 
num being farther advanced downwards than any other 
bone of the wrifi. Its bafe is a broad fuperficial cavity, 
flanting outwards; the internal pofterior angle of which is 
fo prominent, as to have the appearance of a procefs. The 
motion of this bone is very little more than that of the for¬ 
mer; and therefore thefe two firmly refill bodies prefled 
againfl them by the thumb or fingers, or both. Os meta¬ 
carpi digiti annularis is fhorter than the fecond metacarpal 
1 O M Y. 55 a 
-hone. . Its bafe is femicircular and convex, for its eon- 
jundlion with the os unci forme. On its internal 1 fide are 
two fmooth convexities, and a middle folFa,~ adapted to 
the fecond metacarpal bone. The external fide has a tri¬ 
angular fmooth concave furface, to join it with the fourth 
one. Os metacarpi minimi digiti is the f’malleft and fharpeft. 
Its bafe is irregularly convex, and riles flanting outwards. 
Its internal fide is exaftly adapted to the third metacarpal 
bone. The external has no fmooth furface, becaufe it is 
not contiguous to any other bone; but it is prominent 
where the extenfor carpi ulnaris is inferted. As this me¬ 
tacarpal bone is furnifhed with a proper moving mufcle, 
has the plained articulation, is molt loofely connected and 
lead confined, it not only enjoys a much larger motion 
than any of the reft, but draws the third bone with it, 
when the palm of the hand is made hollow by its ad¬ 
vancement forwards, and by the prominence of the thumb 
oppofite to it. 
Ti;e thumb , and fingers, are each compofed of three 
bones. The thumb is fituated obliquely in refpett of the 
fingers ; and ali its bones are much thicker and flronger in 
proportion to their length. The find bone of the tluimb 
has its-bafe adapted to the double pulley of the trape¬ 
zium ; for, in viewing’it from'one fide to the other, it ap¬ 
pears convex in the -middle; but, when confidered from 
behind forwards, it is concave there. The articulation of 
the upper end of this bone is uncommon ; for, - though it 
has protuberances and depressions adapted to the double 
pulley of the trapezia if), yet it enjoys a circular motion, 
as.the joints do where a round head of the one plays in 
the orbicular focket of another ; only it is fomewhat more 
confined, and lefs expeditious, but Itronger and more fe- 
cure, than fitch joints'generally are. The fecond bone of 
the thumb has a large bafe formed into an oblong cavity, 
whofe greatefl length is from one fide to the other. Round 
it feveral tubercles may be remarked, for .the infertion of 
ligaments. Its body is convex or a half-round behind ; 
but flat before, for lodging the tendon of the long flexor, 
of the thumb, which is lied down by ligamentous (heaths 
that are fixed on each fide to the angle .it the edge of this 
flat furface. The-articulation and motion of the upper 
end of this fecond bone is as Angular as that of the- former. 
For, its cavity being joined to the round head of the firfi 
bone, it would feem to enjoy motion in all directions; yet-, 
becaufe of the ftrength of its lateral ligaments, oblong fi¬ 
gure of'the joint itfelf, and mobility of the firfi joint, if 
.only allows flexion and extenfion, and thefe are generally 
much confined. The third bone of the thumb is the fmall¬ 
efi, with a large bafe, whofe greatefl extent is from one 
fide to the other. This bafe is formed into two cavities 
and a middle protuberance, to be adapted to the pulley of 
the .former bone. Its body is rounded behind ; but is flatter 
than in the former bone for fuftaining the - nail. It is flat 
and rough before, by the infertion of the flexor tevtii in- 
ternodii. The motion of this third bone is confined to 
flexion and extenfion. 
The orderly difpofitiotn of the bones of the fingers into 
three rows, has made them generally obtain the name of 
three phalanges. All of them have half-round convSx fur- 
faces, covered with an aporieurofis, formed by the tendons 
of the extenfors, lumbricales, and interoflei, and placed 
diredly backwards, for their greater ftrength ; and their 
flat concave part is forwards, for taking hold more furely, 
and for lodging the tendons of the flexor mufcles. The 
ligaments for keeping down thefe tendons are fixed to the 
angles that are between the convex and concave fides. The, 
bones of the firfi phalanx of the fingers anfvver to tire de- 
feription of the fecond hone of the thumb ; only that the 
cavity in their bafe is not fo oblong; nor is their motion 
on the metacarpal bones fo much confined ; for-they can 
be moved laterally or circularly but have no rotation, or 
a very fmali degree of it, round their axis. The fecond 
bone of the fingers has its hafe formed into two lateral 
cavities, and a middle protuberance; while the lower-end 
has two lateral protuberances and a middle cavity; there. 
