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 orzgiu 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.—(1) 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). 
JInsertions.—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 which comes from the lateral cuneiform 
has its zzsertion 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. J/nsertzon into the outer side of the base 
of the first phalanx of the second digit. It is an adductor 
medius digiti secundi. 
