240 OSTEOLOGY. 
downwards; this rests on the central articular surface on the anterior aspect of — 
the navicular. In front the bone articulates by means of a wedge-shaped facet 
with the base of the metatarsal bone of the second toe. 
The external or third cuneiform (os cuneiforme tertium) intermediate in size 
between the first and second, is also of a typical wedge shape. Its superior surface, 
shehtly convex from side to 
side, provides attachments for- 
the dorsal ligaments. Its 
inferior or plantar aspect is 
narrow and tubercular, and 
serves for the attachment of 
the plantar ligaments. Its 
inner side, of quadrilateral 
form, displays two narrow 
articular strips, placed along 
its anterior and posterior 
borders respectively, each 
somewhat constricted in the middle. The anterior articulates with the outer side 
of the base of the second metatarsal bone, the posterior with the outer side of 
the middle cuneiform. The rough non-articular surface, which separates the two 
elongated facets, serves for the attachment of ligaments. The outer aspect of the 
bone is characterised by a large circular or oval facet, placed near its hinder border, | 
for articulation with the cuboid; in front of this the anterior border is lipped above 
by a small semi-oval facet for articulation with the inner side of the base of the 
fourth metatarsal. The rest of the bone around and between these facets is rough 
for ligaments. Proximally the bone is furnished with a triangular facet for 
articulation with the outer wedge-shaped area on the front of the navicular, whilst 
distally it articulates with the base of the third metatarsal by a surface of corre- 
sponding shape. 
MIDDLE CUNEIFORM CuBOID IV. METATARSAL 
METATARSAL 
NAVICULAR 
II. METATARSAL 
JAE Ee 
Fic. 186.—Ricat EXTERNAL Fic. 187.—RiIcHt EXTERNAL 
CUNEIFORM (Inner Side). CUNEIFORM (Outer Side). 
> 
e- cer = = 
# 
| 
. é 2 . opie a . “pp . 
Variations.—Numerous cases of division of the internal cuneiform bone into dorsal and — 
plantar parts have been recorded; the frequent division of its metatarsal articular facet is no 
doubt correlated with this Srna condition. 
THE CuBOID BONE. 
The cuboid (os cuboideum) lies on the outer side of the foot, about its middle, 
articulating with the os calcis behind and the fourth and fifth metatarsal bones in~ 
front. Its uv pper surface, plane in an antero-posterior direction, is slightly rounded — 
from side to side, and provides attachment for ligaments. Its plantar aspect is 
traversed obliquely from without inwards and forwards by a thick and prominent 
ridge, the outer extremity of which, at the point where it is confluent with the 
outer surface, forms a prominent tubercle (tuberositas oss. cuboidei), the anterior 
and external surface of which is smooth and faceted to allow of the play of a 
sesamoid bone NAVICULAR 
W h ie h 18 fr e= EXTERNAL CUNEIFORM (occasional) 
quently developed 
in the tendon of 
the  peroneus 
longus muscle. 
In front of this 
ridge there is a 
groove (sulcus 
Os CALCIS 
METATARSAL 
TV. METATARSAL 
Os CALCIS 
Vi 
eae : / : 
peronel) in which TUBEROSITY GROOVE FOR PERONEUS GROOVE FOR TUBEROSITY 
the tendon of the ade TK, Bh OTM ES 
peroneus longus Fra. 188.—THE RicHr CuBoip BONE. 
muscle is lodged A. Outer Side. 
as it passes across 
the under surface of the bone. Behind the ridge the bone is rough, and serves for 
the attachment of the short plantar ligament, the superficial fibres of which pass 
B, Inner Side. 
