480 DR. R. W. SHUFELDT ON [NoV. 16, 



After we have cut away tlie tibialis anticus, we fiod another, aud 

 only cue other, muscle occupying the anterior aspect of the tibia. 

 This is the extensor longus digitorum. 



The extensor longus digitorum (Plate XLV. fig. 1, e.l.d) arises 

 from the anterior aspect of the in-half of the tibial shaft as high up 

 as the tibialis anticus muscle, which covers it ; it also arises from a 

 tense fascia which comes off from the lower free edge of the pro- 

 cnemial crest of the tibia ; and finally from a lon^itadinal line ex- 

 tending obliquely down the front of the shaft of the tibia to its 

 lower tliird. This obliquity finally brings the tendon in which the 

 extensor longus digitorum terminates to the middle line. 



Just above the condyles of the tibia, it here passes through the 

 little bony bridge ; emerging from which it crosses the ankle-joint in 

 front, then passes down the anterior aspect of the tarso-metatarsus 

 bone, overlying the short extensor. At the upper end of this last- 

 named bone, and over the ankle-joint, this tendon is firmly bound 

 down by a fibrous fascia. In some birds we know a special bony 

 span exists for it on the upper part of the tarso-metatarsus, as in 

 certain Owls. When the tendon of this muscle arrives at the 

 anterior aspect of the trochleae of the distal end of the tarso-meta- 

 tarsus, it expands and bifurcates. The tendinous expansion becomes 

 more or less attached to the underlying tissues, while each bifur- 

 cation passes one over the second, and the other over the third toe, 

 for their entire lengths, to become inserted into the upper points of 

 their ungual phalanges. 



Now from the side of the tendon that goes to the third toe 

 another slip is differentiated off in a very peculiar manner, owing to 

 the reversion of the toe in question. For it not only passes over the 

 top length for insertion of this fourth digit, as in the case of the 

 others, but its slip also splits off to make a separate insertion at the 

 extremity of the basal phalanx of the third digit. I have had the 

 opportunity of dissecting three feet, with the view of studying this 

 point, and I find it to obtain in all of them. 



The extensor brevis digitorum (Plate XLV. fig. 1, e.h.d). This is a 

 muscle I find that, in common with many other authors, I have de- 

 scribed in my MSS. as the extensor hallucis brevis, from the fact that 

 its tendon goes to the hallux alone. But here, so extraordinary is its 

 development, that no such term would be either adequate or appro- 

 priate. 



Even here the short extensor of the hallux has a certain amount 

 of individualization, though it is not fully differentiated from the 

 other part of this extensor brevis. It, however, is not attached 

 more than halfway down the anterior aspect of the shaft of the 

 tarso-metatarsus, at which point it terminates in a dehcate thread- 

 like tendon ; this passes directly over the upper border of the 

 accessory metatarsal, and along the top of the basal joint of the 

 hallux, to become inserted in the usual manner in the base of the 

 claw-joint. Now the remainder of the extensor brevis digitorum is 

 attached down the shaft of the tarso-metatarsus, as far as the distal 

 trochleae ; the outer portion of it developing a tendon about halfway 

 down, which is concealed by the carueous fibres which overlie it. 



