362 THE MUSCLES. 



Muscles of the Leg. 



These muscles, nine in number, are grouped around the two principal bonea 

 of the leg, so as almost to completely envelop them, leaving only the internal 

 face of the tibia uncovered. Like those of the forearm, they form two particular 

 regions : an anterior and a posterior ; and they are sheathed in common by the 

 tibial aponeurosis — a very solid fibrous covering, which in every respect corresponds 

 to the antibrachial aponeurosis. 



Tibial Aponeurosis. 



This aponeurosis is formed of several superposed layers which are intimately 

 united, and receives, superiorly, the insertion of the biceps femoris, the semi- 

 tendinosus, and the gracilis, which may be considered as its tensor muscles. 



It is continued, inferiorly, over the tarsus and the metatarsal region, in 

 becoming singularly attenuated, and in covering the fibrous bands which bind 

 and retain the anterior tibial muscles in the bend of the hock. Its external 

 surface is separated from the skin by a very thin fibrous expansion ; its internal 

 face furnishes special and very firm sheaths around the majority of the tibial 

 muscles. 



The tibial aponeurosis is attached to the internal surface and crest of the 

 tibia, as well as to the summit of the calcis. The latter attachment takes place 

 by a thick fibrous band, the singular and complicated arrangement of which 

 has not yet been exactly described. It is situated in front of the tendon of the 

 gastrocnemius, or between that tendon and the deep layer of the posterior tibial 

 muscles. By its borders, it is continuous with the tibial aponeurosis or fascia. 

 Superiorly, it adheres most intimately to the perforatus tendon, near the point where 

 the latter originates ; then it sends off a thick fasciculus that descends to the 

 gastrocnemius tendon. Below this, it appears to divide into two branches — an 

 external and internal — which are united to the calcanean cap of the perforatus 

 tendon, and are attached to the sides of the os calcis in such a manner, that 

 near its insertion the gastrocnemius tendon is found to be enveloped by a complete 

 fibrous sheath, formed partly by the perforatus tendon and partly by the band 

 just described. This latter, therefore, constitutes a strengthening apparatus for 

 the tendon of the gastrocnemius — a structure noticed by Girard, who made it a 

 branch of insertion of the semitendinosus ; and not without reason, perhaps, 

 because it arises from the tibial aponeurosis, which, in part at least, is itself 

 derived from the semitendinosus muscle. 



Preparation of the Muscles of the tegr.— Separate the limb from the trunk by sawing through 

 the femur at its middle. Dissect the insertions of the superficial gluteus, the biceps femoris, 

 the gracilis, and the semitendinosus, to observe the continuity of these muscles with the 

 tibial aponeurosis : study the insertions of this aponeurosis, particularly that which it has on 

 the summit of the os calcis. To expose the muscles, remove their aponeurotic envelope, leaving, 

 however, the band it forms in front of the tendon of the gastrocnemius, as well as the bands 

 •which retain the tendons. Eemove the hoof in the manner already indicated for the anterior 

 extremity, and, finally, separate the muscles from one another — an operation so very simple 

 as not to require any special directions. 



A. Anterior Tibial Region. 

 This is composed of three muscles : the flexor of the metatarsus, the anterior 

 extensor, and the lateral extensor of the phalanges. The first is deep-seated, the 

 other two are superficial. 



