304 THE SKELETON. 



the existence of a deep groove on its under surface, for the tendon of the Peroneus 

 longus muscle. It presents for examination six surfaces : three articular and 

 three non-articular. 



The non-articular surfaces are the superior, inferior, and external. The 

 superior or dorsal surface, directed upward and outward, is rough, for the attach- 

 ment of numerous ligaments. The inferior or plantar surface presents in front a 

 deep groove, which runs obliquely from without, forward and inward ; it lodges 

 the tendon of the Peroneus longus, and is bounded behind by a prominent ridge, 

 to which is attached the long calcaneo-cuboid ligament. The ridge terminates 

 externally in an eminence, the tuber osity of the cuboid, the surface of which 

 presents a convex facet, for articulation with the sesamoid bone of the tendon 

 contained in the groove. The surface of bone behind the groove is rough, for the 

 attachment of the short plantar ligament, a few fibres of the Flexor brevis hallucis, 

 and a fasciculus from the tendon of the Tibialis posticus. The external surface, 

 the smallest and narrowest of the three, presents a deep notch formed by the 

 commencement of the peroneal groove. 



The articular surfaces are the posterior, anterior, and internal. The posterior 

 surface is smooth, triangular, and concavo-convex, for articulation with the 

 anterior surface of the os calcis. The anterior, of smaller size, but also irregu- 

 larly triangular, is divided by a vertical ridge into two facets : the inner one, 

 quadrilateral in form, articulates with the fourth metatarsal bone ; the outer one, 

 larger and more triangular, articulates with the fifth metatarsal. The internal 

 surface is broad, rough, irregularly quadrilateral, presenting at its middle and 

 upper part a smooth oval facet, for articulation with the external cuneiform bone ; 

 and behind this (occasionally) a smaller facet, for articulation with the navic- 

 ular ; it is rough in the rest of. its extent, for the attachment of strong interosseous 

 ligaments. 



To ascertain to which foot the bone belongs, hold it so that its under surface, 

 marked by the peroneal groove, looks dow r nward, and the large concavo-convex 

 articular surface backward toward the holder : the narrow non-articular surface, 

 marked by the commencement of the peroneal groove, will point to the side to 

 which the bone belongs. 



Articulations. With four bones : the os calcis, external cuneiform, and the 

 fourth and fifth metatarsal bones ; occasionally with the navicular. 



Attachment of Muscles. Part of the Flexor brevis hallucis and a slip from 

 the tendon of the Tibialis posticus. 



The Navicular. 



The Navicular or Scaphoid bone is situated at the inner side of the tarsus, 

 between the astragalus behind and the three cuneiform bones in front. It 

 may be distinguished by its form, being concave behind,, convex and subdivided 

 into three facets in front. 



The anterior surface, of an oblong form, is convex from side to side, and sub- 

 divided by two ridges into three facets, for articulation with the three cuneiform 

 bones. The posterior surface is oval, concave, broader externally than internally, 

 and articulates with the rounded head of the astragalus. The superior surface is 

 convex from side to side, and rough for the attachment of ligaments. The 

 inferior is irregular, and also rough for the attachment of ligaments. The internal 

 surface presents a rounded tubercular eminence, the tuberosity of the navicular, 

 the lower part of which projects, and gives attachment to part of the tendon of 

 the Tibialis posticus. The external surface is rough and irregular, for the 

 attachment of ligamentous fibres, and occasionally presents a small facet for 

 articulation with the cuboid bone. 



To ascertain to which foot the bone belongs, hold it with the concave articular 

 surface backward, and the convex dorsal surface upward ; the external surface 

 i. e. the surface opposite the tubercle will point to the side to which the bone 

 belongs. 



