Chap, xxiii.] THE ANKLE AND FOOT. 467 



portions is, however, of some substance, and forms a 

 very thick band between the os calcis and fifth meta- 

 tarsal bone, that may become rigidly contracted in 

 some forms of talipes. The central expansion assists 

 greatly in supporting the antero-posterior arch of the 

 foot, which it tends to maintain in the manner that 

 the bowstring maintains the arch of the bow. 



The sinking of the arch that occurs in "flat foot" 

 is associated with marked yielding of this fascia. 

 The plantar fascia is often found much contracted (as 

 a rule, secondarily) in certain forms of club-foot, 

 such as talipes equinus and congenital varus. The 

 term " talipes cavus " is applied to a deformity 

 that depends mainly or entirely upon a contraction 

 of the plantar fascia. The best place in which to 

 divide this membrane is at a spot about one inch in 

 front of its attachment to the os calcis. This is its 

 narrowest part, and the knife (which should be 

 introduced from the inner side) will be behind the 

 external plantar artery which runs beneath the ex- 

 pansion. An abscess situated beneath the membrane 

 will be very closely bound down, and will advance 

 in any direction other than through the membrane 

 itself so as to point in the centre of the sole. Such 

 deep collections cause intense pain, and often much 

 destruction, before they are discharged. They may 

 open upon the dorsum, or may extend up along the 

 tendons to the region of the ankle. There are certain 

 foramina or spaces in the substance of this layer 

 occupied usually by fat. Through one or more of 

 these an abscess will, in exceptional cases, extend, and 

 then spread out beneath the integuments. Such an 

 abscess will have, therefore, two cavities united by 

 a small hole, and will form the abces en bissac or 

 en bouton de chemise of the French. The plantar 

 fascia divides into slips near the roots of the toes, and 

 forms a series of arches, beneath which pass the 



