Chap, xxiii.] THE ANKLE AND FOOT. 



523 



3. The dislocation upwards. In this rare accident 

 the inferior tibio-fibular ligaments are ruptured, the 

 two bones are widely separated at their lower ends, 

 and the astragalus is driven up between them. The 

 anterior and posterior ligaments are entirely rup- 

 tured, but the lateral ligaments usually escape with 

 but some slight laceration. The accident appears to 

 be generally caused by a fall, the patient alighting flat 

 upon the soles of the feet. Mr. Bryant records a case 

 in which both feet were similarly dislocated upwards. 



The foot. There are two arches in the foot, an 

 antero-posterior and a transverse. 



1. The antero-posterior arch has its summit at the 

 astragalus. It may be considered as composed of 



Fig. 55. Antero- Posterior Section of the Foot (Rttdinger). 



1, Tibia ; 2, astrarolua : 3, os calcis ; 4, scaphoid : 5. int. cuneiform ; 6, flrst 

 niftatarsal bone ; 7 and 8, pliulangee of great toe. 



two piers. The hinder pier consists of the os calcis, 

 the anterior pier of the scaphoid, cuneiform and 

 metatarsal bones. The astragalus forms the keystone 

 of the arch, the head of the bone especially perform- 

 ing that function (Fig. 55). 



