DISSECTION OF THE LOWER EXTREMITY 177 



The medial part is the weakest. It is continuous posteriorly 

 with the ligamentum laciniatum, and is attached along the medial 

 margin of the foot to the tarsal and first metatarsal bones. What 

 muscles does this part cover! 



The lateral part is stronger than the medial. It is attached 

 behind to the lateral tubercle of the os calcaneum and in front 

 to the tuberosity and the lateral border of the fifth metatarsal. 

 Posteriorly all three divisions give origin to muscles. 



From the deep surface of the plantar aponeurosis a medial 

 and a lateral process are given off, which pass downward to fuse 

 with the fascia interossea plantaris and to become attached to the 

 tarsal bones. Three separate muscular compartments are thus 

 formed. These septa may be seen if the plantar aponeurosis be 

 incised in the median line from heel to toe and reflected each way. 



Contraction of the plantar fascia gives rise to the condition 

 known as pes cavum. The division of the aponeurosis is most 

 easily accomplished one inch in front of its attachments to the 

 os calcaneum, where it is narrowest. Pus may collect beneath 

 the fascia, and it is apt to burrow, because the aponeurosis is so 

 dense that pus cannot perforate it. Occasionally pus may pass 

 through one of the small foramina formed by the passage of 

 small arteries and nerves through the aponeurosis. In this case 

 two abscess-cavities will be formed. Such a condition is known 

 as the abces en bissac. 



Eemove the aponeurosis plantaris and study the structures 



beneath. 



FIG. 72. 



J M. flexor dig. 



M. flexor hall, long 



Caput plantare 



\\< 



/ 



J 2 



Relation of the tendons of the M. flexor digitoruin longus and of the M flexor halhieis longus x*n 

 from the upper side. (From Gegenbaur, Lehrb. der Anat. des Mensch., Leipzig, 1H99, / 

 Fig. 339.) 



Superficial Layer of Muscles of the Sole. (Vide Spalteholz, Fig. 398.) 

 Note the form, position, origin, insertion, action, and inner- 



vation of each. 



12 



