MYOLOGY OF THE ORNITHORHYNCHUS . 169 



leg, passes at first obliquely across the middle of the instep, and 

 thence more laterally to gain the great toe, upon the surface of which 

 it runs to the base of the ungual phalanx. It is a large muscle, 

 wholly superficial, and, like the tibialis anticus, is partly separable 

 into tibial and fibular heads of origin. 



Extensor " longus !" digitorum. — Smaller than either of the muscles 

 upon the direct front of the leg, with a short belly and a long tendon ; 

 it is deep-seated, covered over by the preceding, and in apposition 

 with the peroneal muscles proper. Its origin is wholly fibular, by a 

 short, stout tendon, from a tubercle on the articular head of the fibula, 

 and it lies wholly upon this bone. Its long slender tendon passes a 

 little obliquely down upon the fibula, then along the groove between 

 the bone and the tibia, just internal to the tendon of the next de- 

 scribed muscle. On the instep it spreads into a fan-shaped fascial 

 expansion that covers most of the dorsum, and is then difl'erentiated 

 into 4 tendons that supply, in the usual way, all the digits except the 

 great toe. 



Extensor '■'brevis !" digitorum. — This Is the muscle that in man oc- 

 cupies the instep; here carried up the leg; not, however, as in opos- 

 sum, etc., to form a peroneal muscle passing behind the outer mal- 

 leolus, but coming obliquely down the leg in front, crossing the fibula 

 below, gaining the groove between this bone and the tibia, alongside 

 the tendon of the foregoing. The muscular part is the most deep- 

 seated of aoy on the front of the leg, and the smallest of all ; a thin 

 little plane arising from, and lying upon the expanded surface of the 

 fibula opposite and a little above the articular head of this bone. 

 The tendon that it soon forms is flat, and, with the course just men- 

 tioned, spreads, after passing the ankle, into a large fan-shaped plane, 

 similar to, and lying underneath the plane of extensor longus. It is 

 difiicult of being distinguished into tendons, but with some care may 

 be demonstrated to proceed to all five digits, and nearly or quite 

 to their tips. In its digital course, it is closely connected with the 

 sheath of the toes, and it runs rather along their sides than directly 

 upon their dorsal aspects. 



Extensor minimi digiti. Peroneus tertius. — The third peroneal or 

 fiexor tarsi fibularis of anthropotomy is a muscle of considerable 

 size, that lies upon the extensor "brevis" digitorum, on the front of 

 the fibula, and is overlaid by the p. longus. It is a flattened strip 

 that arises fleshy from the crest of the fibula and contiguous anterior 

 surface, narrowing regularly as it descends, and becoming tendinous 

 a little below the middle of the leg. Crossing the tendon of p. longus, 

 its tendon gains the outer border of the foot, at base of the 5th meta- 

 tarsal, and thence runs along the little toe to be inserted into the 

 base of its ungual phalanx. It is an abducting extensor of that digit. 



This muscle, which, in man, is inconsiderable and appears like an ofl- 



