480 SURGICAL APPLIED ANATOMY. [Chap. xxui. 



The foot rests upon the heel, the heads of the 

 metatarsal bones, and the outer margin of the foot. 

 The hinder pier is solid, is made up of two strong 

 bones, and contains only one joint. It serves to 

 support the main part of the weight of the body, and 

 gives a firm basis of attachment to the muscles of the 

 calf. The anterior part of the arch, on the other 

 hand, contains many small bones and a number of 

 complicated joints. It serves to give elasticity to the 

 foot, and to diminish the effect of shocks received 

 upon the sole of the foot. The comparative value of 

 the two piers of the arch in this latter respect can be 

 estimated by jumping from a height and alighting 

 first upon the heels and then upon the balls of the 

 toes. The inner part of the arch is much more 

 curved than the outer, and forms the instep. 



2. The transverse arch is most marked across the 

 cuneiform bones. It gives much elasticity to the foot 

 and affords protection to the vessels of the sole. 



These two arches result from the shape of the 

 component bones, and are maintained by the various 

 ligaments. The peroneus longus tendon, and nearly 

 all the ligaments which connect the first and second 

 rows of tarsal bones on both the plantar and dorsal 

 aspects, are inclined forwards and inwards, and by this 

 arrangement are well adapted to maintain the integrity 

 of the transverse as well as of the antero-posterior 

 arch. 



The chief joints of the foot. The articu- 

 lation between the os calcis and astragalus forms 

 a double joint. The posterior joint, that behind the 

 interosseous ligament, has a separate synovial sac, 

 while the anterior communicates with the synovial 

 cavity of the mid-tarsal articulation. The two bones 

 are held together not only by the interosseous, the 

 internal, external, and posterior calcaneo-astragaloid 

 ligaments, but are supported also by the external 



