492 



MYOLOGY 



by a thin layer of fascia. It arises by a narrow tendon, from the medial process 

 of the tuberosity of the calcaneus, from the central part of the plantar aponeurosis, 

 and from the intermuscular septa between it and the adjacent muscles. It passes 

 forward, and divides into four tendons, one for each of the four lesser toes. Oppo- 

 site the bases of the first phalanges, each tendon divides into two slips, to allow of 

 the passage of the corresponding tendon of the Flexor digitorum longus; the two 

 portions of the tendon then unite and form a grooved channel for the reception 

 of the accompanying long Flexor tendon. Finally, it divides a second time, and 



is inserted into the sides of the second phalanx 

 about its middle. The mode of division of the 

 tendons of the Flexor digitorum brevis, and of 

 their insertion into the phalanges, is analogous 

 to that of the tendons of the Flexor digitorum 

 sublimis in the hand. 



Variations. Slip to the little toe frequently wanting, 

 23 per cent.; or it may be replaced by a small fusiform 

 muscle arising from the long flexor tendon or from the 

 Quadratus plantse. 



Fibrous Sheaths of the Flexor Tendons. The 

 terminal portions of the tendons of the long 

 and short Flexor muscles are contained in 

 osseoaponeurotic canals similar in their ar- 

 rangement to those in .the fingers. These 

 canals are formed above by the phalanges 

 and below by fibrous bands, which arch across 

 the tendons, and are attached on either side 

 to the margins of the phalanges. Opposite 

 the bodies of the proximal and second pha- 

 langes the fibrous bands are strong, and the 

 fibers are transverse; but opposite the joints 

 they are much thinner, .and the fibers are 

 directed obliquely. Each canal contains a 

 mucous sheath, which is reflected on the con- 

 tained tendons. 



The Abductor digit! quinti (Abductor minimi 

 digiti) lies along the lateral border of the foot, 

 and is in relation by its medial margin with 

 the lateral plantar vessels and nerves. It arises, 

 by a broad origin, from the lateral process of 

 the tuberosity of the calcaneus, from the under 

 surface of the calcaneus between the two pro- 

 cesses of the tuberosity, from the forepart of 

 the medial process, from the plantar aponeu- 

 rosis, and from the intermuscular septum 

 between it and the Flexor digitorum brevis. Its 

 tendon, after gliding over a smooth facet on the 

 under surface of the base of the fifth metatarsal bone, is inserted, with the 

 Flexor digiti quinti brevis, into the fibular side of the base of the first phalanx 

 of the fifth toe. 



Variations. Slips of origin from the tuberosity at the base of the fifth metatarsal Abductor 

 ossis metatarsi quinti, origin external tubercle of the calcaneus, insertion into tuberosity of the 

 fifth metatarsal bone in common with or beneath the outer margin of the plantar fascia. 





FIG. 443. Muscles of the sole of the foot. 

 First layer. 



