THE rooT. 281 



becomes blended posteriorly witli the corium of tbe skin 

 of the heels, and laterally receives the termination of the 

 coronary fibrous band. The apex extends to within about 

 one inch of the toe of the os pedis. The lateral parts 

 superiorly are separated from inner surface of the lateral 

 cartilage by means of a plexus of veins ; inferiorly are 

 firmly attached to the inflections of the cartilages, the 

 transition between the two structures being gradual. The 

 inferior surface presents a figure analogous to that of the 

 under surface of the horny frog, which is moulded upon 

 it with the intervention of the vascular frog. It therefore 

 presents two hulbs separated from each other by a cleft, 

 which form the base, and which converge anteriorly, 

 and are continued forward to terminate in a point, the 

 aj^ex. 



We now come to the basement structure of the foot, 

 the several parts composing which we must now examine. 

 The bones in the foot are, os pedis, os navicular e, and the 

 inferior extremity of os coronce. 



OS CORONA, though broader than long, and possessing 

 no medullary canal, is generally considered to be a long 

 round bone. It really consists but of two extremities. Its 

 superior extremity articulates with the inferior articulatory 

 surface of os suffraginis, and thus presents a smooth sur- 

 face coated with articular cartilage, consisting of two 

 shallow concavities, the inner of which is the largest. 

 These are separated by a slight prominence, extending in an 

 antero-posterior direction ; the articulatory surface taken 

 as a whole is concave from before backwards, and the 

 prominence terminates posteriorly in a projecting point. 

 The inferior extremity articulates with the os pedis and os 

 naviculare ; thus it presents a smooth surface which is broad 

 jDOsteriorly, and at the anterior part terminates in a point, 

 to which the coronal process of the os pedis is adapted. 

 The surface presents two prominences separated by a 

 shallow groove ; the inner division is slightly the largest. 

 The posterior surface of the bone superiorly presents a pro- 

 minence extending from the inner to the outer surface, 

 which superiorly is roughened for attachment of the long 

 inferior sesamoideal ligament, and below this presents a 

 smooth surface coated with articular cartilage, lubricated 

 with synovia, over which the flexor pedis perforans plays 

 immediately after passing between the two terminal divi- 



