METATARSO-PHALANGEAL JOINTS. 651 



rating forcibly the cuneiform bones from one another and from the os 

 cuboides ; the latter bone from the os scaphoides : 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 two lateral and an inferior ligament, as in the 

 hand; and the joint is further strengthened above by an expansion derived 

 from the tendons of the extensors of the toes. A distinct synovial mem- 

 brane exists in each joint. 



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

 are connected with the inferior and lateral ligaments. 



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

 distinct; and their anatomy is more fully described with the dissection of 

 that part. (See page 301.) 



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

 longest from above down, and reachest 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 un- 

 der the head of the metatarsal bone ; and when it is extended 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 fore part of the lateral ligaments, and by the extensor tendon ; and 

 to extension, by the tightness of the inferior, and the hinder 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 phalangeal 

 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 recognized in these articulations. The 

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

 small bones are immovably united by osseous substance. These ligaments 

 receive a more particular notice with the dissection of the hand (p. 302). 



A simple synovial membrane exists in each phalangeal articulation. 



Articular surfaces. In both phalangeal joints, the nearest phalanx 

 presents a trochlear surface; and the distal one is marked by two lateral 

 hollows or cups with a median ridge. 



Movement. Only flexion and extension are permitted in the two pha- 

 langeal joints of the toes, as in the hand. 



Inflexion the farther phalanx glides under the nearer; and in extension 

 the two are brought into a straight line. 



The bending is checked by the lateral ligaments and the extensor ten- 

 don; and the straightening is limited by the inferior ligament and the 

 flexor tendons. 



