232 



DISSECTION OF THE LEG. 



Separate the 

 bones to see 

 interosseous 

 ligaments. 



Union of 

 metatarsus 

 and pha- 

 langes, by 



two lateral 

 ligaments, 

 and inferior: 

 synovial 

 sac. 



Form of 

 bones. 



Kind of 

 motion. 



Bending 

 and extend- 

 ing, 



state of 

 ligaments : 



lateral 

 motion 



circular 

 motion 

 limited. 



Union of the 

 phalanges. 



Synovial 

 sac. 



Dissection. All the superficial ligaments having been taken 

 away, the interosseous ligaments of the tarsus and metatarsus may 

 be seen by separating forcibly the cuneiform bones from one another 

 and from the cuboid, the latter bone from the navicular, and the 

 bases of the metatarsals from one another. The dissector will find 

 that, in using force, the bones will sometimes tear sooner than the 

 ligaments. 



METATARSUS WITH PHALANGES. These are condyloid joints, in 

 which the head of the metatarsal bone is received into the cavity 

 of the phalanx. 



Each articulation has an inferior and two lateral ligaments, as in 

 the hand ; and the joint is further strengthened above by an ex- 

 pansion derived from the tendons of the extensors of the toes. A 

 distinct synovial sac exists in each joint. 



In the articulation of the great toe there are two sesamoid bones, 

 which are connected with the inferior ligament. 



All these structures are better seen in the hand, where they are 

 more distinct ; and their anatomy has been more fully described 

 with the dissection of that part. (See pp. 104 and 105.) 



Surfaces of bone. The metatarsal bone has a rounded head, which 

 is longest from above down, and reaches farthest on the plantar 

 surface. On the end of the phalanx is a cup-shaped cavity. 



Movement. In this condyloid joint, as in the hand, there is 

 angular motion in four different directions, with circumduction. 



Flexion and extension. When the joint is bent, the phalanx 

 passes under the head of the metatarsal bone ; and when it is ex- 

 tended, the phalanx moves back beyond a straight line with the 

 metatarsal bone. 



A limit to flexion is set by the meeting of the bones, by the 

 stretching of the upper part of the lateral ligaments, and by tl it- 

 extensor tendon ; and to extension, by the tightness of the inferior, 

 and the lower part of each lateral ligament, and by the flexor 

 tendons. 



Lateral movement. The phalanx passes from side to side across 

 the end of the metatarsal bone. Its motion is checked by the 

 lateral ligament of the side from which it moved, and by the 

 contact with the other digits. 



Circumduction, or the revolving of the phalanx over the rounded 

 head of the metatarsal bone, is least impeded in the great toe 

 joint ; but these movements in the foot are not so free as in the 

 hand. 



ARTICULATIONS OF THE PHALANGES. There are two interpha- 

 langeal joints to each toe, except the first. 



Ligaments similar to those in the metatarso-phalangeal joints, viz., 

 two lateral and an inferior, are to be recognised in these articulations. 

 The joint between the last two phalanges is least distinct ; and 

 oftentimes the small bones are immovably united by osseous sub- 

 stance. These ligaments receive a more particular notice with the 

 dissection of the hand (p. 105). 



A simple synovial membrane exists in each phalangeal articulation. 



