1872.] LATELY LIVING IN THE SOCIETY'S COLLECTION. 361 



round the anterior half, and the gastrocnemius posticus, which sur- 

 rounds the back part of the tibial section of the limb. Gastrocne- 

 mius anticus arises partly from the tibia, partly by blending with 

 gastrocnemius posticus ; the latter arises from the distal extremity 

 of the femur, the tendon of the quadriceps extensor and patella, and 

 from 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 gastro- 

 cnemius posticus), 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 perfo- 

 ratus. Gastrocnemius anticus is inserted into the posterior surface 

 of the tarso-metatarsal bone just below the tibio-tarsal joint. Gas- 

 trocnemius 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. 



Flexor magnus arises (1) by a tendon from the upper part of the 

 external surface of the outer condyle of the femur, the tendon wind- 

 ing 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 eud 

 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- 

 tended ; there is a smaller " sesamoid " cartilage for the external 

 digit. A small muscle arises from the larger cartilage and by a few 



* Alexander Macalister, L.R.C.S.I., Demonstrator of Anatomy, Royal College 

 of Surgeons. " On the Anatomy of the Ostrich (Sfruthio camelus)," Proceedings 

 of the Royal Irish Academy, vol. ix. part 1 (1865). 



