MUSCULAR SYSTEM OF MAMMALIA. 37 



lower down than in the human subject, a circumstance which 

 causes the leg to be permanently kept in a semiflexed condition. 



The ( gastrocnemius,' fig. 11,6, is relatively less carneous than in 

 Man : the f solaeus ' is slender and feeble : but the ' plantaris,' fig. 

 12, 13, is remarkably developed ; it arises from the fossa above the 

 external femoral condyle: its tendon, is, is continued down ward, and 

 runs over the extremity of the os calcis, where it is enclosed in a 

 sheath; passing on from this point, it divides, is, to be inserted upon 

 each side of the posterior surface of the proximal phalanx towards 

 its inferior extremity, here giving passage between its two inser- 

 tions to the tendon of the long flexor of the toe, which it serves 

 to bind down closely to the pastern when the fetlock joint is bent, 

 thus seeming to perform the functions both of the ( plantaris ' and 

 of the short flexor of the toes. 



The 'tibialis anticus,' fig. 12, 37, is implanted into the anterior 

 surface of the base of the metatarsal, so as to be an extensor of 

 that portion of the foot. The ( tibialis posticus ' is seen at 25 and 

 2t>, fig. 12. The c popliteus,' ib. 23, is a powerful muscle. The 

 three s peronei ' are represented by a single muscle, the tendon 

 of which becomes conjoined with that of the long extensor of 

 the digit, with which, when in action, it co-operates. The 

 flexor muscles are reduced to a state of extreme simplicity ; the 

 short flexor communis is wanting ; the ( plantaris,' as described 

 above, has a double insertion into the base of the great pastern 

 bone, and presents a similar disposition to that of the flexor per- 

 foratus in digitate quadrupeds, while the f flexor communis longus 

 perforans,' fig. 12, 28, here serving a single tendon, 29, appropriated 

 to the solitary toe, passes on as usual to be inserted into the last 

 phalanx, so, 31. The homologue of the ' flexor longus hallucis' 

 exists in the Horse, notwithstanding the absence of the hallux ; 

 but, instead of its usual destination, it here becomes affixed to the 

 tendon of the flexor communis perforans, to which it forms a 

 powerful auxiliary. 



The ' extensor communis,' fio;. 11, 21, terminates in a single 



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tendon, 25, which is inserted into the dorsum of the last phalanx 

 of the foot : it receives, however, in its course, a few fleshy fibres, 

 w, derived from the metacarpal and representing the * extensor 

 brevis ' of unguiculate quadrupeds. 



In fio\ 14, showing the chief ligaments of the hind limb, are 



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represented the ( iliacus interims/ /, k, I, and the ( epicotyloideus,' 

 <7, a small and peculiar muscle, which arises by a flat tendon, b, 

 from above the origin of the rectus cruris, d, and is inserted at the 

 fore and outer part of the neck of the femur, c, below the head : 



