REGIONAL ANATOMY 15 
The Lateral Ligaments——These are large and thick, an 
outer and an inner, running obliquely from above down- 
wards and backwards. Each is inserted superiorly into 
the lateral tubercle of the lower end of the first phalanx, 
and inferiorly to the side of the second phalanx, their most 
inferior fibres becoming finally fixed to the extremities of 
the navicular bone, where they form the postero-lateral 
ligaments of the pedal articulation. In front of the joint 
the extensor pedis plays the part of an additional ligament. 
The Synovial Membrane.—This is limited in front by the 
tendon of the extensor pedis, on each side by the lateral 
ligaments of the joint, and behind by the glenoid fibro- 
cartilage. At this point it is prolonged upwards as a pouch 
behind the lower extremity of the first phalanx. 
Tue ARTICULATION OF THE SECOND PHALANX WITH THE 
THrrD, THE PEDAL, oR THE Corrin Jomnt.—This also is an 
imperfect hinge-joint, permitting only of flexion and exten- 
sion, which movements are more restricted than in the 
previous articulation. Three bones enter into its forma- 
tion: the second phalanx, the third phalanx, and the 
navicular bone. The lower articulatory surface is formed 
by the third phalanx and the navicular bone combined. 
To effect this the navicular is closely and firmly attached 
to the third phalanx by an interosseous ligament. The 
two bones, as one, are then connected to the second phalanx 
by four lateral ligaments, an anterior and a posterior on 
each side. 
The Interosseous Ligament consists of extremely short 
fibres running from the extensively grooved portion of the 
anterior surface of the navicular bone to become attached 
to the os pedis immediately behind its articular surface. 
The Antero-lateral Ligaments are attached by their 
superior extremities to the lateral surfaces of the second 
phalanx, and by their inferior extremities into the depres- 
sions on either side of the pyramidal process of the 
os pedis. 
The Postero-lateral Ligaments.—As mentioned when 
describing the first interphalangeal articulation, these are 
