ANATOM Y. 
it feems to have a very good title to a third, the rotula ; 
which bears a ftrong analogy to the olecranon of the ulna, 
and moves always with the other two. 
The tibia, fo called from its refemblance to an old mu- 
fical pipe or flute, is the long thick triangular bone, fitu- 
Ated at the internal part of the leg, and continued in al- 
moft a firaight line from the thigh-bone. The upper end 
of the tibia is large, bulbous, and fpongy, and is divided 
into two cavities by a rough irregular protuberance, which 
is hollow at its moil prominent part, as well as before and 
behind. The anterior of the two ligaments that compol’e 
the great crofs one is inferted into the middle cavity, and 
the deprellion behind receives the pofterior ligament. The 
two broad cavities at the tides of this protuberance are 
not equal; for the internal is oblong and deep, to receive 
the internal condyle of the thigh-bone ; while the exter¬ 
nal is more fuperficial and rounder, for the external con¬ 
dyle. In each of thefe two cavities of a recent fubjedt, 
a femilunar cartilage is placed, which is thick at its con¬ 
vex edge, and becomes gradually thinner towards the 
concave or interior edge. The middle of each of thefe 
cartilages is broad, and the ends of them turn narrower 
and thinner as they approach the middle protuberance of 
the tibia. The thick convex edge of each cartilage is con¬ 
nected to the capfular and other ligaments of the articula¬ 
tion ; but fo near to their rife from the tibia, that the 
cartilages are not allowed to change place far; while the 
narrow ends of the cartilages, becoming almoft ligaments, 
are fixed at the infertion of the ftrong crofs ligament into 
the tibia, and teem to have their fubftance united with 
it; therefore a circular hole is left between each cartilage 
and the ligament, in which the moll prominent convex 
part of each condyle of the thigh-bone moves. The cir¬ 
cumference of thefe cavities is rough and unequal, for the 
firm connection of the ligaments of the joint. 
Below the fore-part of the upper end of the tibia, a 
confiderable rough protuberance rifes, to which the ftrong 
tendinous ligament of the rotula is fixed. On the internal 
fide of this, there is a broad fcabrous (lightly-hollowed 
furface, to which the internal long ligament of the joint, 
the aponeurofis of the vaftus interims, and the tendons of 
the feminervofus, gracilis, and fartorius, are fixed. The 
loweft part of this furface is therefore the place where the 
tibia ought to be fawn through in an amputation, fo as 
not to have too long and troublefome a (lump, and at the 
fame time to preferve its motions, by having the proper 
mufcles. Below the external edge of the upper end of 
the tibia, there is a flat circular furface, .covered in a re¬ 
cent fubjeft with cartilage, for the articulation of the fi¬ 
bula; between which and the anterior knob, a rough hol¬ 
low affords origins to the tibialis anticus and extenfor di- 
gitorum longus. From this fmooth flat furface, a ridge 
runs obliquely downwards and inwards, to give rife to part 
of the folaeus, tibialis pofticus, and flexor digitorum lon¬ 
gus, and infertion to the aponeurofis of the femimembra- 
nofus which covers the poplitaeus, and to fome of the ex¬ 
ternal fibres of this laft-named mufcle. At the infide of 
this ridge an oblique plain furface is left, where the great- 
eft part of the mufculus poplitteus is inferted. The re¬ 
maining body of the tibia is triangular. The anterior an¬ 
gle is very (harp, and is commonly called the /pine, nxjhin. 
This ridge is not ftraight; but turns firft inwards, then 
outwards, and laftly inwards again. T he plain internal 
fide is fmooth and equal, being little fubjedted to the ac¬ 
tions of mufcles ; but the external fide is hollowed above 
by the tibialis anticus, and below by the extenfor digito¬ 
rum longus and extenfor pollicis longus. The two angles 
behind thefe fides are rounded by the adtion of the mufcles; 
the pofterior fide comprehended between them is not fo 
broad as thofe already mentioned, but is more oblique and 
flatted by the adtion of the tibialis pofticus and flexor di¬ 
gitorum longus. A little above the middle of the bone, 
the internal angle terminates, and the bone is made round 
by the preflure of the mufculus folreus. Near to this the 
paffage of the medullary vellels Hants obliquely downwards. 
Vol. I. No. 35. 
The lower end of the tibia is hollowed, fo as to occafion 
a fmall protuberance to fife in the middle. The intern..t 
fide of this cavity, which is fmooth, and in a recent fub- 
jedt is covered with cartilage, is produced into a confide¬ 
rable procefs, commonly named malleolus internus ; the 
point of which is divided by a notch, and from it liga¬ 
ments are fent out to the foot. We ought to obferve here, 
that this internal malleolus is (ituated more forwards than 
the internal condyle of the upper end of this bone ; which 
is necelfary to be remembered in reducing a fradhtre of 
the leg. The external (ide of this end of the tibia has a 
rough irregular femilunar cavity formed in it for receiv¬ 
ing the lower end of the fibula. The pofterior (ide has 
two lateral grooves, and a fmall middle protuberance. In 
the internal depreflion, the tendons of the mufculus tibia¬ 
lis pofticus and flexor digitorum longus are lodged; and, 
in the external, the tendon of the flexor longus pollicis 
plays. From the middle protuberance, ligamentous (heaths 
go out, for tying down thefe tendons. 
Tlte fibula is the fmall long bone, placed on the outfide 
of the leg, oppolite to the external angle of the tibia; 
the lhape of it is irregularly triangular. The head of the 
fibula has a fuperficial circular cavity formed on its infide, 
which, in a recent fubjedl, is covered with a cartilage, and 
it is fo clo(ely connected to the tibia by ligaments, as to 
allow only a fmall motion backwards and forwards. This 
head is protuberant and rough on its outfide, where a ftrong 
round ligament and the mufculus biceps are inferted ; and, 
below the back-part of its internal (ide, a tubercle may be 
remarked, that gives rife to the ftrong tendinous part of 
the folaeus mufcle. The external furface of the fibula is 
deprefled obliquely from above downwards and backwards 
by the two perontei. Its internal furface is unequally di¬ 
vided into two narrow longitudinal planes, by an oblique 
ridge extended from the upper part of the anterior angle, 
to join with the lower end of the internal angle. To this 
ridge the ligament ftretched between the two bones of the 
leg is connected. The anterior of the two planes is very 
narrow above, where the extenfor longus digitorum and 
extenfor longus pollicis arife from it; but is broader be¬ 
low, where it has the print ot the nonus Vefalii. The 
pofterior plane is broad and hollow, giving origin to the 
larger (hare of the tibialis pofticus. The internal angle 
of this bone has a tendinous membrane fixed to it, from 
which fome fibres of the flexor digitorum longus take 
their rife. The pofterior furface of the fibula is the plain- 
eft and fmootheft; but is made flat above by the folaeus, 
and is hollowed below by the flexor pollicis longus. In 
the middle of this furface, the canal for the medullary 
veffels may be feen (lanting downwards. 
The lower end of the fibula is extended into a fpongy 
oblong head; on the infide of which is a convex,' irregu¬ 
lar, and frequently a fcabrous, furface, that is received by 
the external hollow of the tibia, and fo firmly joined to it 
by a very thin intermediate cartilage and ftrong ligaments, 
that it can fcarcely move. Below this the fibula is ftretch¬ 
ed out into a fmooth coronoid procefs, covered with carti¬ 
lage on its internal fide, and is there contiguous to the 
outfide of the firft bone of the foot, the aftragalus, to fe¬ 
cit re the articulation. This procefs, named malleolus cx- 
temus, being (Ituated farther back than the internal mal¬ 
leolus, and in an oblique direction, obliges us naturally 
to turn the fore-part of the foot outwards. At the low¬ 
er internal part of this procefs, a fpongy cavity for muci¬ 
laginous glands may be remarked; from its point ligaments 
are extended to the aftragalus, os calcis, and os nav-.cu- 
lare, bones of the foot; and from its infide fhort ftrong 
ones go out to the aftragalus. On the back part of it a 
fmuollty is made by the tendons of the peroruei mufcles. 
When the ligament extended over thefe tendons from the 
one fide of the depreflion to the other is broken, ftretched 
too much, or made weak by a fprain, the tendons fre¬ 
quently ft art forwards to the outfide of the fibula. 
Rotula is the fmall flat bone (ituated at the fore-part of 
the joint of the knee. Its fhape refembles the common 
j C figure 
