IN THE SOCIETY’S COLLECTION. 103 
Flezor digiti interni arises from the outside of the tubercle of the 
tibia, and from the tendon of the quadriceps extensor; the tendon 
passes through the gastrocnemial sheath and the sesamoid pulley. It 
pierces the flexor magnus, receiving a tendinous slip from it, and then 
spreads ont and binds the tendon of the flexor profundus to the grooved 
under surface of the second phalanx of the internal digit, and is in- 
serted by two slips into the proximal end of the third phalanx. 
Flexor digiti externi arises from the posterior surface of the distal 
end of the femur, and from the tendinous head of flexor magnus. It 
passes through the gastrocnemial sheath, pierces the tendon of flexor Page 363. 
magnus, passes through the lesser sesamoid sheaths, and is inserted 
into each of the three proximal phalanges of the external toe. 
Flezor profundus arises by two heads—one from the posterior sur- 
face of distal end of femur, the other from the posterior surface of the 
upper half of the tibia and part of the fibula. The tendon of the 
external muscle passes at the tibio-tarsal joint through a canal in the 
tendon of gastrocnemius anticus. The inner tendon does not enter 
the gastrocnemial sheath till below the joint; it passes down the inner 
surface of the contiguous ends of the tibia and the tarso-metatarsal 
bone, bound down to them by a special aponeurotic sheath, and joins 
the outer tendon near the tarso-phalangeal joint. The common tendon 
- passes over the sesamoid pulley, piercing the flexor magnus tendon ; 
it is here much thickened and hardened, and fits into the grooved 
and thickened tendon of flexor perforans. It is inserted into the 
fourth phalanx of the internal toe, sending off a short strong slip 
to the third phalanx, and an elastic slip to the second phalanx, as 
well as a small but long slip to flex the fifth phalanx of the external 
digit. 
Mr. Macalister describes the tendon of the flexor profundus as being 
inserted only into the last phalanges of both digits; the insertion as 
it was in my specimen accords, I believe, with the usual condition of 
this tendon in birds. 
The flexor interosseus is a delicate and weak muscle, which con- 
sists of numerous very short oblique fibres arising from the posterior 
surface of the tarso-metatarsal bone, and inserted into an aponeurosis 
stretching the whole length of the muscle; this aponeurosis ends in 
a tendon which is inserted into the outer surface of the first phalanx 
of the external digit. Its action appears to be to abduct and flex the 
‘ toe. 
| A small muscle which Mr. Macalister does not describe, but merely 
: mentions as probably representing the dorsal interosseus, arises from a 
small triangular space on the anterior surface of the distal end of the 
tarso-metatarsal bone, and is inserted into the capsular ligament of 
the tarso-phalangeal joint. There were some differences between the 
a ee 
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