866 THE MUSCLES. 



the movement it is supposed to prevent. And experiment clearly shows that we 

 are justified in this opinion ; for division of this tendon in the living animal 

 does not interfere in the slightest degree with its natural attitude, either when 

 standing at liberty or when compelled to stand.^ 



B. Muscular Portion. — Situation — Form — Structure. — Situated between 

 the tendinous cord and the tibia, this portion is elongated from above to below, 

 very wide at its superior part and narrow inferiorly, where it terminates in a 

 bifid tendon. 



Attachments. — It originates, by the upper extremity of its muscular fibres, 

 from the tibia, below and on the sides of the groove through which the tendon 

 passes ; its most superficial fibres are even attached to the aponeurotic sheath 

 which envelops the lateral extensor. Its terminal tendon (Fig. 201, 6) traverses 

 the annular ligament which the tendinous portion forms at its inferior extremity, 

 and becomes inserted, by one of its branches, in front of the superior extremity 

 of the principal metatarsal bone, along with the analogous branch of the 

 tendinous division (Fig. 200, 8). The other ramification is directed to the 

 inside of the tarsus, to be attached to the second cuneiform bone (Fig. 202, 7). 



Relations. — In front, with the tendinous portion of the muscle and the 

 anterior extensor of the phalanges ; behind, with the external face of the tibia. 

 The tendon, after traversing the annular ligament of the cord, covers the 

 metatarsal branch of the latter, and is in turn covered by the anterior extensor. 



Action. — It is an active agent in flexing the foot on the leg. 



B. Posterior Tibial Region. 



This region includes six muscles, which are arranged in two superposed 

 layers behind the tibia. The superficial layer is formed by the gastrocnemii, 

 soleus or plantaris, and the superficial flexor of the phalanges. The deep layer is 

 composed of the popliteus, the deep flexor, and the oblique flexor of the phalanges. 



• J. F. Meckel rightly considers this tendinous cord, not as a portion of the anterior tibial, 

 but as a dependency of tlie extensor longus digitorum. It would be wrong, however, to 

 describe it apart fioin the anterior tibial, properly so-called— that is, the muscular portion of 

 our flexor metatarsi, the two being, in their action, essentially one. 



Is there anything in the human species analogous to this fibrous cord? After much 

 hesitation, we answer in the affirmative, and give it as our opinion that this tendon represents 

 the peroneus tertius in Man. These are our reasons tor making tliis assertion, hazardous as it 

 certainly is at first sight: In Man, the peroneus tertius cannot always be easily distinguished 

 from the extensor loiigus digitorum ; so that these two muscles may be regarded as a single 

 one until reaching the instep, where it extenda to the phalanges of the toes on the one part, nnd 

 the metatarsus on the other. Precisely the same arrangement is found in Solipeds ; the single 

 muscle divides into two fasciculi, one for the digital region (anterior extensor of the phalanges), 

 the other to the metatarsal region (tendon of our flexor metatarsi). This tendon, then, exactly 

 represents the fasciculus of the long common extensor of the toes (in Man), which goes to the 

 metatarsus, and is designated the peroneus tertius. 



But to this it may be said : Your peroneus tertius in the Horse has no relation whatever to 

 the peroneus, and does not this prove that you are in error? No ; for if this muscle is attached 

 to the fibula in Man, it is because the principal muscle on which it depends is inserted there 

 itself. But as the anterior extensor of tlie phalanges of the Horse— that is, the common 

 extensor of the toes— is not inserted into the fibula, and has no connection with it in any way, 

 its metatarsal fasciculus— or rather its tendinous cord or peroneus tertius— ought to be absolutely 

 in the same condition. We repeat, however, that this opinion may be, perhaps, a little 

 hazardous ; and we give it with reserve, though we have some reasons for considering it to be 

 correct. 



