DISSECTION OF THE LOWER EXTREMITY 179 



Proper digital plantar nerves (Nn. digitales plantar -es 



proprii). 

 (bb) Deep branch (ramus profundus). 



Second Layer of Muscles and Tendons of the Sole. 



(a) Tendons of the M. flexor digitorum longus. 



(aa) Quadrate muscle of the sole (M. quadratics plantae) (0. T. 



accessorius muscle). (Fig. 72.) 



Two planes of fibres will be found in this muscle. Dis- 

 sect both out carefully and determine their relations to the 

 different tendons. 



(ab) Lumbrical muscles (Mm. lumbricales) . Determine the exact 



modes of origin from the tendons of the long flexor and 

 trace them forward to the tendons of the long extensor. 

 These little muscles act chiefly through the above tendons 

 and produce, when active, a flexion of the first phalanx and 

 extension of the second and third. Dissect out the bursae 

 Mm. lumbricalium pedis. 



(b) Tendon of the long flexor of the great toe. Determine the relative 



position of this tendon and dissect out the tendinous process pass- 

 ing over to the tendon of the long flexor of the digits. 



Divide the tendons of the M. flexor longus digitorum, M. 

 flexor longus hallucis, M. quadratus plantae, and the plantar ves- 

 sels and nerves near the os calcaneum and reflect them down- 

 ward. 



Third Layer of Muscles of the Sole. (Vide Spalteholz, Fig. 400.) 



(a) Short flexor muscle of great toe (M. flexor hallucis brevis). 



(b) Adductor muscle of great toe (M. adductor hallucis). 



(ba) Oblique head (caput obliquum). 



(bb) Transverse head (caput transversum). 



(c) Short flexor muscle of fifth toe (M. flexor digiti quinti brevis). 



(d) Opposing muscle of little toe (M. opponens digiti quinti). 



Sever the M. flexor digitorum brevis and the caput obliquum 

 of the M. adductor hallucis at their origins and reflect them 

 downward. Complete now the study of the arcus plantaris. De- 

 termine where the deep branch of the dorsal artery of the foot 

 passes into the planta. Note the deep branch of the lateral 

 plantar nerve close by the arch. 



Displace the digital vessels and nerves forward and sever t 

 short flexor of the little toe and the transverse head of 

 adductor hallucis at their origins and reflect. Note the strong 

 bands of fibrous tissue (ligamentum capitulorum transversum) 

 passing between the heads of the metacarpal bones. 



