276 SURGICAL ANATOMY OF 



It is superficial, but is bound down by a very dense 

 aponeurosis, which must be divided cautiously to avoid 

 injuring the artery beneath. An incision is to be made 

 over the instep along the outer border of the extensor 

 proprius pollicis, when the vessel will be found lying in 

 a triangular interspace formed by the outer border of 

 the extensor proprius pollicis internally, by the inner 

 tendon of the extensor brevis externally, and by the 

 fleshy fibres of the extensor brevis digitorum, poste- 

 riorly. The nerve lies to its outer side. 



SURGICAL ANATOMY OF THE SOLE OF THE FOOT. 



Dissection. On removing the integument, which is 

 very thick and strong, the first tissue met with is a 

 dense layer of fat, in which are three bursse, one beneath 

 the os calcis, and two beneath the heads of the first and 

 fifth metatarsal bones. Ramifying in the fat are some 

 cutaneous branches of the cutaneous nerves of the foot, 

 some perforating branches of the plantar vessels, and a 

 great number of lymphatics. The next layer is formed 

 by the plantar fascia, consisting of three portions, of 

 which the central is the strongest, sending down pro- 

 cesses which inclose the several muscles, separating the 

 middle from the external and plantar groups. The 

 fascia divides opposite the middle of the metatarsus into 

 five processes, each one of which divides again opposite 

 the metatarso-phalangeal joint into two slips, which by 

 their deep attachments form arches for the passage of the 

 flexor tendons to pass to the toes ; the interspace allows 

 of the digital vessels and nerves, the tendons of the 

 lumbricales and interossei becoming superficial. The 

 mutual relations of the structures forming the sole of 



