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IN THE SOCIETY’S COLLECTION. 101 
the tibia. At the tibio-tarsal joint the gastrocnemii form a sheath 
fitting into the trochlea of the tibia for the passage of the flexor ~ 
tendons of the toes; this is effected by the tendons becoming very | 
much thickened and semicartilaginous (especially gastrocnemius pos- 
ticus), and uniting with each other at their edges, the anterior element 
of the sheath being formed by gastrocnemius anticus, the posterior by 
gastrocnemius posticus. Just above the joint, gastrocnemius anticus 
sends off a slip which passes down in a special sheath along the outer 
surface of the contiguous heads of tibia and tarso-metatarsal bone, and 
is inserted into the tendon of flexor perforatus. Gastrocnemius anti- 
cus is inserted into the posterior surface of the tarso-metatarsal 
bone just below the tibio-tarsal joint. Gastrocnemius posticus is 
inserted into the external and internal lips of the posterior border of 
the tarso-metatarsal bone, forming a sheath for the passage of the 
flexor tendons; it subsequently forms, with a “sesamoid”’ cartilage 
presently to be described, a pulley for the same tendons at the tarso- 
_ phalangeal joint, and ends by blending with the fascia covering the 
sole of the foot. Mr. Macalister* describes the gastrocnemius as 
ending in one tendon only, which he says forms a sheath for the 
deeper tendons on the back of the metatarsus. 
The flexors of the toes are flexor magnus (perforatus), flexor per- 
forans, flexor externi digiti, flexor interosseus, flexor profundus. 
Flezor magnus arises (1) by a tendon from the upper part of the 
external surface of the outer condyle of the femur, the tendon winding 
over the knee, and then ending in the muscle; just before it does so, 
it receives the insertion of the rectus femoris (Cuvier and Meckel), 
(the pectineus of Owen); (2) from posterior surface of distal end of 
femur; (3) proximal end of tibia. The muscle ends in a broad 
tendon, which passes through the gastrocnemial sheath at the tibio- 
tarsal joint, and is here pierced by the tendon of flexor externi digiti. 
It passes down the tarso-metatarsal bone in the sheath formed by 
gastrocnemius posticus, receiving a tendinous slip, already described, 
from gastrocnemius anticus. At the tarso-phalangeal joint it passes 
through a sheath formed anteriorly by a “‘sesamoid” cartilage, 
posteriorly by the tendon of gastrocnemius posticus. This cartilage 
is ligamentously attached to the proximal end of the first phalanx of 
the internal digit, and to the synovial membrane of the tarso-pha- 
langeal joint ; it is deeply grooved posteriorly for the flexor tendons, 
and has two shallow grooves on its anterior surface, which fit on to 
the condyles of the tarso-metatarsal bone when the digits are ex- 
* Alexander Macalister, L.R.C.S.I., Demonstrator of Anatomy, Royal College 
of Surgeons, “On the Anatomy of the Ostrich (Struthio camelus),” “ Proceedings 
of the Royal Irish Academy,” IX. Part 1 (1865). 
