OSTEOLOGY. 81 



surface is convex from side to side, and is mainly occupied 

 by tlie extensor pedis tendon with the bands running to it 

 from the superior- sessamoideal ligament. It is, therefore, 

 smooth for the most part, but above and below it becomes 

 roughened. Superiorly it is ]3rominent for attachment of 

 the tendon of extensor suffraginis (or ligamentum exten- 

 sorum). This prominence is slightly inclined to the outer 

 side. The ijosterior surface is also convex, and superiorly 

 presents externally and internally two prominent angles 

 from which two ridges converge to form a prominent rough 

 surface at the central part, to which the short part of the 

 inferior sessamoideal ligaments is attached. To the angles, 

 are attached white fibrous bands, which converge in be- 

 coming attached to the posterior surface of the perforatus 

 tendon ; they are parts of the annular ligament of the fet- 

 loch. The margins of this bone lie in contact with the plantar 

 vessels and nerves, and inferiorly present a roughened line, 

 to which the superior ligament of the navicular bone is at- 

 tached in blending with the lateral hgament of the pastern 

 joint. The superior articulatory surface of the bone is in 

 every respect concave, and presents three concavities, the 

 inner and outer of which are triangular; the inner is shghtly 

 the largest. The central concavity is deepest and narrowest, 

 extending from the anterior to the posterior surface, while 

 between "it and the above-mentioned ridges is a rougher 

 space perforated by numerous foramina. The inferior ex- 

 tremity is much smaller than the superior, and presents an 

 irregularly heart-shaped articulation, which, by uniting 

 with the upper extremity of os coronse, fonus the pastern 

 joint. This is obtusely rounded anteriorly, extending 

 shghtly on to the anterior surface, and consists of two 

 roimded convexities, which meet forming a shallow groove. 

 They extend considerably on to the posterior surface, and 

 are here separated by a roughened indentation ; the inner 

 is slightly the largest. On either side, slightly inclined to 

 the anterior part, just above the articulation, the lateral 

 ligaments of the pastern are attached. Posteriorly, above 

 the articulatory surface, are numerous foramina. 



Ossa coronse, pedis, and naviciilare will be examined in 

 dissection of the foot. 



