THE LOWER EXTREMITY,- POSTERIOR. 641 



Insertion. Into the outer margin and upper surface of 

 the tendon, of the flexor longus digitorum. 



Nerve Supply. The external plantar. 



Action. To convert the oblique pull of the flexor 

 longus digitorum into a direct one, and thus assist in flex- 

 ing the four outer toes. Acting alone, or when the flexor 

 longus digitorum is blocked by the full extension of the 

 ankle, it will still flex the toes. 



The Lumbricales. Four in number. Fig. 133. 



Origin. Arise from the clefts between the tendons of 

 the flexor longus digitorum (being attached to two adja- 

 cent tendons excepting the most internal, which arises from 

 the inner margin of the internal tendon). 



Insertion. Into the aponeurotic expansion of the tendon 

 of the extensor longus digitorum at the inner side of the 

 four outer toes. 



Nerve Supply. The two (sometimes only one) inner 

 muscles are supplied by the internal plantar, the two 

 (sometimes three) outer are supplied by the external 

 plantar. 



Action. These muscles will flex the first set of pha- 

 langes (as their tendons pass below the centre of motion of 

 the metatarsophalangeal articulations), and extend the last 

 two sets of phalanges (because their tendons are inserted 

 into the tendons of the long extensor muscle above the 

 centre of motion of these articulations). Besides this 

 common action, the internal one will abduct the second 

 toe, and the rest adduct the three outer toes with reference 

 to the middle line of the foot (which passes through the 

 centre of the second toe). 



For the tendons of the flexor longus hallucis and the 

 flexor longus digitorum, see these muscles, page 627. 

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