636 A MANUAL OF ANATOMY. 



Between these fasciculi pass the lumbricales and interossei 

 muscles and the digital vessels and nerves. 



The central portion of the plantar fascia is connected at 

 its margins to the ligaments which cover the under surface 

 of the bones of the foot, by fibrous septa, the external and 

 internal intermuscular septa ; these divide the foot into three 

 compartments. 



The lateral portions of the fascia are continuous with the 

 margins of the central portion and pass into the deep fascia 

 covering the dorsum of the foot and the lateral annular liga- 

 ments of the ankle. In addition the external portion has a 

 strong band which extends from the outer surface of the 

 os calcis and the external annular ligament, and is attached 

 to the base of the fifth metatarsal bone, and the internal 

 portion passes from the inner side of the os calcis and inter- 

 nal annular ligament forward, to be inserted into the base 

 of the first phalanx of the great toe. 



DISSECTION. 



Remove the plantar fascia by cutting away altogether the outer and inner 

 portions. Incise the central part transversely about three inches from the 

 heel, raise the anterior portion from the muscle beneath and carefully dissect 

 it forward, dividing the strong intermuscular septum on each side of the mus- 

 cle, until the insertions of the fasciculi are reached. Stop here to examine 

 how the flexor tendons pass through the divided fasciculi while the digital 

 nerves, vessels, and lumbrical muscles lie between the fasciculi themselves, 

 then remove the fascia entirely. Leave the posterior portion attached to the 

 muscle. 



The First Layer. 



The Flexor Brevis Digitorum. Fig. 133. 



Origin. From the anterior part of the greater (inner) 

 tubercle of the os calcis, from the deep surface of the 

 middle portion of the plantar fascia for its posterior third, 

 and from the sides of the intermuscular septa. 



