The Posterior Limb Skeleton. , 109 



dition — is fused with the proximal end of the second metatarsal. The 

 cuboid is a larger element articulating, like the hamate bone of the 

 carpus, with two distal elements, the fourth and fifth metatarsals. Its 

 ventral surface bears a transverse elevation, the tuberosity of the cuboid 

 (tuberositas oss. cuboidei), in front of which is a groove for the accom- 

 modation of the peculiar insertion tendon of the peronaeus primus 

 muscle. 



THE METATARSUS AND PHALANGES. 



The metatarsus (Fig. 43) comprises five elements, of which four are 

 fully developed and greatly exceed in size the corresponding bones of 

 metacarpus, while one, the first metatarsal, is vestigial. The vestigial 

 element lies on the plantar surface of the foot, for the most part ventral 

 to the navicular and at the base of the second metatarsal. In each 

 developed metatarsal there may be distinguished a main portion or body, 

 a proximal extremity or base, and a distal extremity or head, the last- 

 named portion articulating with the proximal phalanx of the digit. The 

 base of the fifth metatarsal bears a tuberosity for the insertion of the 

 peronaeus secundus muscle. 



The phalanges are distributed accordingto the formula 0, 3, 3, 3, 3 

 the terminal, ungual phalanges being modified like those of the anterior 

 limb. 



SESAMOID BONES. 



The sesamoid bones of the posterior limb occur at the knee-joint 

 and on the plantar surface of the foot. On the anterior surface of the knee 

 is the knee-pan or patella, through which, as indicated above, the tendon 

 of the quadriceps femoris muscle is carried over the knee and continued 

 as the patellar ligament to the tuberosity of the tibia. On the posterior 

 surface there are three sesamoid bones, of which one lies in association 

 with the medial condyle of the femur, while the remaining two are asso- 

 ciated respectively with the lateral condyle of the femur and that of the 

 tibia. The sesamoids of the foot are situated at the metatarsophalangeal 

 joints and at those connecting the second and third phalanges. 



