FLEXOR ACCESSORIUS. LUMBRICALES. 



287 



at the posterior aspect of the muscle. The tendon descends in the groove 

 behind the internal malleolus, superficial to the tibialis posticus, and invested 

 by a distinct fibrous and synovial sheath ; it is then directed under the 

 arch of the os calcis, obliquely forwards and outwards, into the sole of 

 the foot, where it crosses below the tendon of the flexor longus pollicis, 

 and is connected with it by a tendiuous slip ; it then divides into four 

 parts, which pass forwards to be inserted into the terminal phalanges 

 of the four smaller toes. Each digital tendon enters a fibrous sheath on 

 the toe for which it is destined, perforates the corresponding tendon of the 

 flexor brevis digitorum, and is invested with synovial membrane, and con- 

 nected by vincula accessoria to the phalanges ; the whole arrangement being 

 exactly similar to that which has been already described as occurring in the 

 fingers. 



The posterior tibial vessels lie upon the surface of the flexor longus digitorum. 



Intimately connected with the tendon of the flexor longus digitorum are 

 the flexor accessorius and the lumbricales muscles, which, although they 

 occupy the foot, may be most conveniently described in this place. 



The flexor accessorius (moles carnea Sylvius) arises by two heads, the 

 internal and larger of which is fleshy, and is attached to the inner surface 

 of the calcaneum, while the external, flat, narrow, and tendinous, is attached 

 to the plantar surface of the calcaneum a little in front of the external 

 tubercle, and to the ligamentum longum plantse. Those origins united form 

 a muscular mass which is inserted into the external border and upper and 

 lower surfaces of the tendon of the flexor longus digitorum. 



Fig. 218. MIDDLE LATER OP THE PLANTAR MUSCLES OP THE 



FOOT, TOGETHER WITH THE TENDONS OP THE LoNQ FLEXOUS 

 AND THE ACCESSORIUS AND LUMBRICALES MUSCLES. 



1, tendon of the flexor longus pollicis muscle, emerging 

 behind from its sheath below the sustentaculuin tali, and 

 passing deeper than, 2, the tendons of the deep common flexor ; 

 3, two heads of the flexor accessorius ; 4, the four lumbricales ; 

 5, tendon of the flexor brevis cut short and left on the second 

 toe, seen splitting to allow the passage through it of the tendon 

 of the long flexor ; 6, flexor brevis pollicis ; 7, flexor brevis 

 minimi digiti ; there is also represented on the outer side of 

 the foot the tendon of the peroueus longus winding round the 

 cuboid bone, to pass across the foot in its groove, where it is 

 concealed by the accessorius and other muscles. 7 



The lumbricales muscles, four in number, arise from 

 the tendons of the flexor longus digitorum at their 

 point of division, each being, with the exception of 

 the most internal, attached to two tendons, and pass 

 forward to the inner sides of the four outer toes ; each 

 muscle ends in a tendon, which is united with the ba c e 

 of the first phalanx, and is inserted into the expansion 

 of the extensor tendon on the dorsum of the toe. 



Fig. 218. 



They 



The lumbricales of the foot are less fully developed than those of the hand, 

 are liable to the same variations. 



In the sole of the foot the tendon of the flexor longus digitorum, together with the 

 flexor accessorius and lumbricales, is covered below by the flexor brevis digitorum ; 

 the plantar nerves and hinder part of the external plantar artery being placed 



