384 THE INFERIOR EXTREMITY 



there it divides into two slips. The two slips embrace the 

 flexor tendons of the toe, and become fixed to the flexor 

 sheaths, and to the transverse ligament of the heads of 

 the metatarsal bones. The general characters, therefore, 

 of the intermediate part of the plantar aponeurosis closely 

 resemble those of the intermediate part of the palmar 

 aponeurosis. 



The lateral and medial parts of the plantar aponeurosis are 

 weak, in comparison with the intermediate portion. They" 

 merely constitute fascial coverings for the muscles which 

 lie subjacent. A strong band is to be noted in connection 

 with the lateral part. It stretches between the prominence 

 formed by the base of the fifth metatarsal bone and the 

 lateral process of the tubercle of the calcaneus. 



In connection with the plantar aponeurosis two inter- 

 muscular septa also have to be studied. These pass dorsally 

 into the sole, along the lines of the longitudinal furrows 

 which mark off the intermediate from the medial and lateral 

 parts of the aponeurosis. They consequently lie one upon 

 each side of the flexor digitorum brevis, and form partitions 

 which separate it from the abductor hallucis on the one side, 

 and the abductor digiti quinti on the other. 



Dissection. To demonstrate the above-mentioned septa, 

 make a transverse incision through the intermediate portion of 

 the plantar aponeurosis, about an inch in front of the medial 

 process of the tubercle of the calcaneus, and also a longitudinal 

 cut through the same piece of aponeurosis, extending from the 

 first incision along the middle line of the foot. Now raise the 

 divided aponeurosis and throw it laterally and medially. Some 

 difficulty will be experienced owing to the deep surface of the 

 aponeurosis affording origin, in its posterior part, to the subjacent 

 flexor digitorum brevis. As the margins of this muscle are 

 approached the septa are brought into view. As the anterior 

 part of the divided aponeurosis is reflected, care must be taken 

 to avoid injury to the plantar digital arteries and nerves which 

 lie close to the deep surface of the aponeurosis. 



Muscles and Tendons of the Sole. It is customary to 

 look upon the muscles and tendons found in the dissection 

 of the sole as being disposed in four strata, in or between 

 which lie the plantar vessels and nerves and their branches, 

 whilst the layers themselves are separated from one another 

 by fibrous partitions, viz. : 



( Abductor hallucis. 



First layer. -! Flexor digitorum brevis. 



^ Abductor digiti quinti. 



