170 ANATOMY OF THE WOOD RAT 



interest to the present contribution lies in its greater or 

 caudal process, extending caudad from the heel, for it is upon 

 the slightly concave termination of this that the tendo 

 Achillis is inserted, and so it plays the role of lever, operated 

 by the great extensors of the foot, and functionally, it is one 

 of the most important osteological features of the leg. The 

 length of this process, measured from the proximal termina- 

 tion of the astragalus, is individually quite variable, which 

 can not be correlated with any other feature. Dorsad there 

 are two facets, separated by a groove, for the articulation 

 of the astragalus. The lower or medial facet is borne upon 

 the sustentaculum, also termed the lesser process, but this 

 name is untenable in the present instance, and had pref- 

 erably be called the medial process. It is well formed, 

 and deeply grooved upon the plantar aspect for the passage 

 of flexor tendons. The more lateral, or tibial facet, is much 

 more prominent and constitutes a well-defined crest upon 

 the bone. Upon the lateral border of the bone is the shelf- 

 like peroneal process, grooved upon the plantar aspect of its 

 border for the passage of the peroneus longus tendon. 

 Distad there is a facet for articulation with the cuboid, 

 while disto-mediad there is articulation with the tarsal 

 sesamoid. The only leg muscles having insertion upon the 

 calcaneum are those connected with the tendo calcaneus, 

 but the quadratus plantae, abductor digiti quinti, and flexor 

 digiti quinti brevis have direct connection with this bone, 

 while the extensor digitorum brevis has origin from the 

 calcaneal ligament. 



The tarsal sesamoid is small, flat, and almost circular in 

 outline. It is situated upon the medial tarsus and articu- 

 lates chiefly with the astragalus and calcaneum, and to a 

 lesser extent with the entocuneiform and scaphoid. Upon 

 it is inserted the tibialis posticus. 



The cuboid is the bone immediately distad to the cal- 

 caneum and is the most lateral one of the distal series of 



