938 OSTEOLOGY. 
also fairly smooth, and is defined inferiorly by an irregular line, sometimes a 
definite ridge, the edges of which are striated. Into this surface the tendo Achillis 
is inserted. The lowest surface is rough and striated, and is confluent below with 
the internal and external tubercles; this is overlain by the dense layer of tissue 
which forms the pad of the heel. 
@ 
Variations. The peroneal tubercle is occasionally unduly prominent, constituting the sub- 
malleolar apophysis of Hyrtl, and cases are recorded of the os calcis articulating with the 
navicular (Morestin, H., Bull. de la Soc. Anat. de Paris, 1894, ser. Were apie ve Ane 05 TSsi and 
Petrini, Att? del XT. C ongr. Med. Internaz. Roma, 1894, vol. 11, & Anat.” p- 7). Phitzner (Morpho- 
logische Arbeiten, vol. vi. p. 245) also records the separation of the sustentaculum tali to form an 
os sustentacull. 
THE NAVICULAR BONE. 
The navicular or scaphoid bone (os naviculare pedis), of compressed pyriform 
shape, is placed on the inner side of the foot, between the head of the astragalus 
posteriorly and the three cuneiform bones anteriorly. The bone derives its name 
MIDDLE CUNEIFORM from the oval or boat- 
shaped hollow on its 
postervor surface, which 
rests upon the head 
of the astragalus. Its 
anterior aspect 1s 
furnished with a semi- 
lunar articular area, 
whichis subdivided by 
EXTERNAL | 
CUNEIFORM / 
JRNAL CUNEIFORM 
OCCASIONAL FACET FOR CUBOID 
TuBERosIty FOR HEAD OF ASPRAGALUS two faint ridges into 
three wedge - shaped 
A B facets for articulation 
Fic. 180.—THe Ricut NavicuLar Bone. from within outwards 
A, As seen from Behind ; B, As seen from the Front. with the internal, 
middle, and external 
cuneiform bones. Swperiorly the surface of the bone, convex from side to side, is 
rough for the attachment of the ligaments on the dorsal aspect of the foot. Inferiorly 
the bone is irregularly concave, and marked by the attachment of the plantar liga- 
ments. The external surface is narrow from before backwards, and rounded from above 
downwards. Usually devoid of any articular surface, it 1s occasionally provided 
with a facet, which rests upon a corresponding area on the cuboid. The inner side 
of the bone projects beyond the general line of the inner border of the foot, so as to 
form a thick rounded tubercle (tuberositas oss. navicularis), the position of which 
can be easily determined in the living. To the inner and under surface of this 
process an extensive portion of the tendon of the tibialis posticus muscle is 
inserted. 
Variations.—Cases are recorded where the tubercle has formed an independent ossicle. 
THE CUNEIFORM BONE 
The cuneiform bones, three in number, are placed between the navicular 
posteriorly and the bases of the first, second, and third metatarsal bones anteriorly, | 
for which reason they are frequently named the first, second, and third cuneiforms, q 
or, from their position, internal, middle, and external. More or less wedge-shaped, 
as their name implies, the internal or first is the largest, whilst the middle or 
second is the smallest of the group. Combined, they form a compact mass, the 
proximal surface of which, fairly regular in outline, rests on the anterior surface of 
the navicular; whilst anteriorly they form a base of support for the three inner | 
metatarsals, the outline of which is irregular, owing to the base of the second 3 
metatarsal bone being recessed between the inner and outer cuneiforms as it 
articulates with the distal extremity of the shorter middle cuneiform 
The internal cuneiform bone (0s cuneiforme primum), the largest of the three, 
lies on the inner border of the foot between the base of the metatarsal bone of the 
