308 TSE MUSCLES. 



loug common extensor of the digits ; 3, A long lateral peroneus ; 4, A short lateral 

 peroneua. . 



1. Anterior tibial. — Situated in front of the tibia, and more voluminous than the 

 common extensor of the digits, whose superior extremity it covers, this muscle has its 

 orin-in on the crest and external tuberosity uf the tibia. It receives, near tlie inferior 

 third of this bone an extremely thin muscular band which proceeds from the fibula, 

 and which we may with justice compare to the proper extensor of the big toe in Jlan. 

 Then it terminates by a tendon on the metatarsal bone of the internal digit; when this 

 bone is connected witli a digital region, the third phalanx receives a particular blanch 

 from this tendon, which represents ihe tendinous portion of the small proper extensor 

 fasciculus annexed to the anterior tibial. This muscle responds : in front to the tibial 

 aponeurosis; inwards and backwards, to tlie tihia; outwards, to the common ex- 

 tensor of the digits. Its tendon is iixed in the bend of the hock by a fibrous band, 

 whose arrangement is singular enough to deserve mention here. Attached in front 

 of the interior extremity of tlie tibia, this band gives origin, by its internal extremity, 

 to a strong ligamentous cord which passes undi-r the tendon of the anterior tibial 

 muscle to reach the anterior face of the tarsus, where it contracts intimate adhesions 

 with the capsular ligament of this region, and terminates on the superior extremity 

 of the metatarsal bone of the middle digit. This cord binds the inferior extremity of 

 the tibia to the metatarsus, and prevents undue extension of the tibio-tarsal articula- 

 tion. It is, perhaps, the representative of the tendinous cord of the anterior tibial region 

 in the Horse. 



2. Long common extensor of the digits. — This muscle is composed of a fusiform fleshy 

 body, and a quadrifurcated tendon. The fleshy body, situated beneath the tibial 

 aponeurosis, between the anterior tibiai and the lateral peroneal muscles, covers the 

 external face of the tibia and the small fasciculus of tlie proper extensor of the thumb; 

 it originates by a short and strong tendinous cord, from the inferior extremity of the 

 femur, between the external condyle and the trochlea. The tendon is continuous with 

 the inferior extremity of the fleshy portion, passes beneath the band of the anterior 

 tibial, through another fibrous ring at the cuboid bone, and is inserted, by its four 

 terminal branches into the four large digits, in the same manner as the analogous tendon 

 in tlie fore-limb. 



3. Long lateral peroneus. — This muscle is composed of a very short conical fleshy 

 portion, succeeded by a long tendon. The former originates in front of the tuberosity of 

 the supero-exteriial tuberosity of the tibia, and- does not appear to have any connection 

 with the fibula. Included between the common extensor of the digits and the short 

 lateral peroneus, it is covered by the tibial aponeurosis, and covers the anterior tibial 

 vessels. The tendon descends parallel with the fibula to its inferior extremity, over which 

 it glides in becoming inflected. On reaching the cuboides, it enters a groove excavated 

 on its external surface, gives off a short isolated branch to the superior extremity of the 

 first metiitarsal bone, afterwards crosses transversely the direction of the tarsus in 

 passing behind the inferior row of bones, and terminates on the metatarsus of the 

 tliumb. On its way behind the cuboides, this tendon gives ofl' another branch which 

 •we have every reason to believe is constantly present; it is a short, interosseous fasci- 

 culus, which at first penetrates between the cuboides and the external metatarsal bone, 

 then between tlie latter and the second metatarsal. 



This muscle carries the inferior extremity of the limb outwards, and when the 

 foot is mufh extended it may act as a flexor. 



4. Short lateral peroneus. — In Cainivora, this muscle is formed of two fasciculi, a 

 superior and inferior, which may be described as two distinct muscles. 



The superior fasciculus comprises a very weak muscular portion attached to the 

 upper third of the anterior border of the fibula, and a funicular tendon succeeding its 

 inferior extremity about the midille of the tibia. This tendon glides over the inferior 

 extremity of the fibula, behind the long lateral peroneus, which it passes under and 

 crosses in descending to the phalanges of the exti-'rnal digit, where it is united to the 

 tendinous branch of the common extensor belon<;ing to this digit. 



The inferior fasciculus has its origin on the anterior border and external aspect of 

 the peroneus, by penniform fibres which join a short, but more voluminous tendon than 

 that of the preceding fasciculus. This tendon, with the last, enters the posterior 

 groove in the fibula, and is attached, by its inferior extremity, to the upper end of the 

 external metatarsus, outside the branch furnished by the long lateral peroneus to that 

 bone. 



The superior fasciculus acts as a proper extensor of the external digit. The inferior 

 is an abductor of the foot. 



