214 THE MUSCLES. 



tendon of the flexor brevis which pass to the three lateral 

 digits, at their entrance to the first annular ligament. The 

 one to the fifth digit is sometimes absent. 



The other three have origin from the tendon of the flexor 

 longus digitorum at the point where it divides. Each occupies 

 one of the three intervals between the four divisions, and its 

 fibres originate from the proximal ends of the two tendons 

 which bound its interval. 



Insertion by a very slender tendon into the medial side of 

 the first phalanges of the third, fourth, and fifth digits near 

 their bases. 



Action. Move the third, fourth, and fifth digits toward the 

 medial side. 



Mm. interossei. The interosseus of the second digit forms 

 five portions, which cover the ventral surface of the digit. 



Origin. (i) By two tendons from the ventral process of 

 the lateral cuneiform. The muscle divides into four parts, three 

 of which pass to the medial side of the digit and act as 

 abductors. They are called the long, short, and middle 

 abductors (abductor longus, brevis, and intermedius digiti 

 secundi). 



Insertions. The short head into the medial sesamoid of 

 the metatarsophalangeal joint, the middle into the medial side 

 of the base of the first phalanx, and the long into the extensor 

 communis tendon near the distal end of the first phalanx. 

 The names long, short, and middle refer to the lengths of the 

 tendons as determined by their points of insertion. 



The fourth portion w r hich comes from the lateral cuneiform 

 has its insertion into the lateral side of the extensor tendon 

 near the distal end of the first phalanx. It is therefore an 

 adductor longus digiti secundi. In some cases there is an 

 adductor brevis from this same head. 



(2) The fifth part of the interosseus of the second digit has 

 origin from the middle of the ligament covering the peroneal 

 canal, along with the middle adductor of the fifth digit. The 

 two muscles diverge. Insertion into the outer side of the base 

 of the first phalanx of the second digit. It is an adductor 

 medius digiti secundi. 



