J. Playfair McMurricli 



57 



fibularis tendon, but the actual tendon can be traced uninterruptedly 

 onward and, as Dobson states, does not really unite with the flexor 

 fibularis tendon, although the connection between the two may be suffi- 

 ciently strong as to make a practical "union. The tendon then begins 

 to flatten out into a broad band which fades out gradually at the sides 

 into the layer of the plantar aponeurosis with which the plantaris is 

 associated, and eventually associates itself with the flexor brevis hallucis, 

 inserting, in part at least, into the under surface of the cartilaginous 

 spur. 



In the other two mammals which I studied the general arrangement 

 of the two flexors was similar to the above, except that the flexor brevis 

 digitorum did not arise from their tendons. The flexor fibularis (Fig. 

 11, FF) is much the larger of the two muscles and sends tendons to all 

 five digits, while the flexor tibialis, in 

 the cat, unites with the tendon of the 

 flexor fibularis before it divides into 

 the terminal tendons. In the mouse 

 the flexor tibialis (Fig. 11, FT) arises 

 in common with the tibialis posticus 

 and its tendon remains completely 

 separate from that of the flexor fibu- 

 laris and fades out into the plantar 

 fascia. In the cat the muscle has an 

 independent origin from the back of the 

 upper part of the tibia. 



The tibialis posticus has also been described for a large number of 

 forms by Dobson, 83, and I shall indicate only briefly its arrangement in 

 the forms I have studied. In the opossum (Fig. 8, TP) it arises from 

 the upper part of the fibula and from a strong aponeurosis which separ- 

 ates it from the adjacent flexor fibularis, and quickly passes over into 

 a tendon which is continued down the leg, under cover of the tendon of 

 the flexor tibialis, and passing behind the inner malleolus is inserted into 

 the scaphoid bone. In the cat it arises from the upper part of the pos- 

 terior surface of the tibia, becomes tendinous at about the middle of the 

 crus and, passing into the foot in a groove on the inner surface of the 

 tibia, is inserted into the scaphoid. In the mouse (Fig. 11, TP) it also 

 arises from the upper posterior part of the tibia as a muscular mass from 

 which later the flexor tibialis separates. It is a slender muscle, soon be- 

 coming a tendon and inserting into the internal cuneiform bone. 



The fcxor accessorius pedis, although apparently a muscle of the pes, 

 is considered here with the crural flexors, since its affinities are altogether 



Fig. 11. — Transverse section through 

 about the middle of the crus of the 

 Mouse. F, fibula : FF, flexor fibularis ; 

 FT, flexor tibialis : Oe, g-astrocnemius 

 lateralis; (H, ffastrocnemius medialis; 

 PI, plantaris ; pf , posterior tibial nerve ; 

 S, soleus; T, tibia, TP, tibialis posticus. 



