88 



THE OSTEOLOGY AND MYOLOGY 



ponding depression in the os calcis, and finally a prominent ridge opposing the concavity 



of the navicular. 



The OS calcis (fig. 27, d) is very large and stout. It projects far back, terminating in a 

 roughened knob for attachment of the tendo Achillis. Upon the plantar surface a promi- 

 nent, stout, straight ridge runs along the median line from the posterior extremity. This 

 ridge, with the help of a process from the astragalus, defines the groove for the digital 

 flexor tendons, and divides the plantar surfiice of the bone into two large, smooth faces, 

 rising obliquely on either side and spreading, or flaring, to support the expanded rotular 

 aspect of the bone. The latter is very irregular, both in contour and superficies. It pre- 

 sents a prominent tubercle, which fits a facet on the under surfiice of the astragalus, and, 

 more internally, a depression corresponding to an elevation on the astragalus. Anteriorly, 

 the bone articulates with the cuboid alone (not with the navicular), by an oblique 

 depressed surface. 



In general terms the navicular (fig. 27, h) may be called hemispherical; but its contour 

 is irregular, being moulded by surrounding bones. There is a deep depression behind and 

 above for the astragalus, and a small, oval facet externally for the cuboid. The three 

 cuneiforms are supported upon a continuous surface — the facet for the internal one being 

 most distinct and decidedly convex ; while the whole surface is convex from side to side. 

 The internal and inferior non-articular surfaces are roughened for the attachment of 

 ligaments. 



The most noticeable feature of the cuboid (fig. 27, e) is the very deep, transverse 

 groove that lodges the tendon of the peroneus longus. There is a deep pit upon the inner 

 face of the bone, just in front of the facet for the navicular. The upper surfiice is nearly 

 plane. Besides the convexity behind for the articulation with the calcis, the cuboid sends a 

 sharp process to meet the plantar ridge of this bone. As usual, the bone supports the two 

 outer metatarsals. The facets are scarcely separated by a ridge ; that ibr the fi)urth mcta- 

 t-arsal is the longest and most cupped ; the other has a slight process overlying the base of 

 the fifth metatarsal. 



Of the three cuneiforms, the outer (fig. 27,/) and middle (fig. 27, g) deserve the name 

 " wedge-shaped," being driven in and locked between the cuboid, inner cuneiform, navicu- 

 lar, and third and second metatarsals. The anterior face of the ecto-cuneiform is not flush, 

 either with that of the cuboid or of the meso-cuneiform, but projects forward. The meso- 

 cuneifi)rm is the shortest and smallest of the three ; it and the ecto-cuneiform both bear 

 simple facets for the corresponding metatarsals. 



The ento-cuneiform (fig. 27, c) is different from the other two, being noticeable for the 

 acute process that assimihites it in physical character to the unciform of the wrist. The 

 bone is of a very irregular shape, difiicult of description, but may be said to have a thick- 

 ened base, by which it articulates largely with the navicular and meso-cuneiform, and 

 from which a stout, curved process is sent forward to overlie the base of the first metatarsal. 

 The articulating surfiice for the latter is narrowly elongate, concavo-convex, with a strong 

 ridge and deep sulcus, reciprocal to inequalities on the head of the metatarsal. The plane 

 of this facet is turned away from the common plane of the others, its degree of obliquity 

 expressing the divergence of the great toe from the rest. While the other tarso-metatarsal 

 articulations arc close, allowing little mobility, and that chiefly in one direction, this one is 



