MUSCLES OF TEE POSTERIOR LIKBS. 301 



Relations. In front, with the anterior extensor of the phalanges; 

 behind, with the muscular portion, and the anterior capsular ligament of 

 the tarsus. 



Action. This tendon enjoys the curious property of bending the hock 

 by an action altogether mechanical, whenever flexion of the superior bones 

 of the limb takes place. It is, therefore, a conducting cord, whose office it 

 is to regulate the movements of flexion in the hock, and conform them to 

 those taking place in the other joints, without requiring the intervention of 

 an active agency for the execution of these movements. 



Another function has also been attributed to it : that of passively opposing 

 the flexion of the femur on the tibia while the animal is standing, and in 

 this way serving as an adjunct to the muscular powers which support the 

 weight of the body. But, in our opinion, this is incorrect ; as in order that 

 it may perform this task, it would be necessary for the foot to be maintained 

 in a fixed position by the contraction of its extensor muscles. But these 

 muscles are really the gastrocnemii, which have their origin behind the 

 femur, and which undoubtedly tend to flex that bone on the tibia that is, to 

 determine the movement it is supposed to prevent. And experiment clearly 

 shows that we are justified in this opinion ; for division of this tendinous cord 

 in the living animal does not interfere in the slightest degree with its 

 natural attitude, either when standing at liberty or when forced to stand. 1 



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 termi- 

 nates in a bifid tendon. 



Attachments. 1 1 originates, by the upper extremity of its muscular fibres, 

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

 tendinous cord passes ; its most superficial fibres are even attached to the 

 aponeurotic sheath which envelops the lateral extensor. Its terminal tendon 

 (Fig. 136, 6) traverses the annular ligament which the tendinous portion 

 forms at its inferior extremity, and becomes inserted, by one of its branches, 



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

 tibial, but as a dependency of the extensor longus digitorum. It would be wrong, 

 however, to describe it apart from the anterior tibial, properly so-called that is, the 

 muscular portion of our flexor of the metatarsus, 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 repre- 

 sents the anterior peroneus (peroneus tertius) in Man. These are our reasons for making 

 this assertion, hazardous as it certainly is at first sight : In Man, the peroneus tertius 

 cannot always be easily distinguished from the extensor longus digitorum ; so that these 

 two muscles may be regarded as a single one until reaching the instep, where it ex- 

 tends to the phalanges of the toes on the one part, and the metatarsus on the other. 

 Precisely the same arrangement is found in Solipeds ; the single muscle divides inio two 

 fasciculi, one for the digital region (anterior extensor of the phalanges), the other to the 

 metatarsal region (tendinous cord of our flexor metatarsi). This tendinous cord, 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 the 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 tins opinion may be, perhaps, a little hazardous ; and we give it with reserve, 

 though we have some reasons for considering it to be correct. 



