TEXDO ACHILLIS. PLANTARIS. 28-5 



Achillis considerably further than those of the gastrocnemius. The posterior 

 surface presents a thin covering of longitudinal aponeurotic fibres continued 

 up from the tendon below, and gliding on the similar tendinous surface of 

 the gastrocnemius muscle. On the deep surface the edges of two mem- 

 branous tendons, the other edges of which look towards the middle line of 

 the muscle, imbedded in its substance, are seen descending from the tibial 

 and fibular origins : the fibres from the deep aspects of those tendons are 

 directed obliquely inwards to a tendinous septum which divides the muscle 

 into lateral halves ; while those from their superficial aspects pass with 

 similar obliquity to the flat tendon on the surface of the muscle, the fibres 

 placed at the sides forming the lateral borders and part of the deep surface 

 of the muscle. Thus the soleus is composed entirely of short oblique fibres 

 of from one to two inches in length. 



The soleus rests upon the flexor longus pollicis, flexor longus digitorum, and tibialis 

 posticus muscles, together with the posterior tibial vessels and nerve, from which, 

 however, it is separated by the deep aponeurosis. 



The Undo Achillis, the thickest and strongest tendon in the body, is 

 formed by the union of the flat tendon of the gastrocnemius with the 

 thicker and more rounded tendon of the soleus. It is from three to four 

 inches long below the point where the muscular fibres of the soleus cease to 

 be attached to it. It is inserted inferiorly into the back part of the 

 tuberosity of the os calcis. Between the upper part of the tuberosity of the 

 os calcis and the tendon a synovial bursa is interposed. 



The gastrocnemius is, in some cases, joined by a bundle of muscular fibres, which 

 arises separately from the femur above one of the condyles. This bundle has been 

 observed passing between the popliteal artery and vein (R. Quain, op. cit. plate 80, 

 figs. 4 and 5). To the soleus an accessory portion is occasionally added at its lower 

 and inner part; this usually ends on the inner side of the tendo Achillis, but it 

 sometimes forms a tendon, attached separately to the os calcia. 



The plantaris arises from the femur immediately above the external con- 

 dyle, and from the posterior ligament of the knee-joint, where this is covered 

 by the corresponding head of the gastrocnemius ; its muscular part is from 

 three to four inches in length, and terminates in a long delicate tendon, 

 which inclines inwards between the gastrocnemius and soleus, and, running 

 along the inner border of the tendo Achillis, is inserted conjointly with it 

 into the posterior part of the calcaneum. 



The designation by which this little muscle is known was assigned to it when the 

 tendon was believed to terminate in the plantar fascia, as the palmaris longus does in 

 the fascia of the hand. It was so described by Galen ; and, though the real manner 

 of termination was correctly pointed out by Vesalius (Oper. 1, 2, p. 419), the error 

 was continued through many succeeding works, and is to be found even in Cowper's 

 "Myotomia Reformata" (p. 105). 



The plantaris varies in its mode of termination ; it is sometimes enclosed in the 

 lower part of the tendo Achillis ; and, in other cases, it ends in the internal annular 

 ligament, which binds down the tendons and vessels behind the inner malleolus. 



The deep group of posterior muscles of the leg is in close contact with 

 the bones ; it consists of the popliteus, flexor longus digitorum, flexor longus 

 pollicis, and tibialis posticus. 



The popliteus, an oblique muscle placed below the knee, arises by a thick 

 tendon, about an inch in length, from the fore part of the popliteal groove 

 on the outer side of the external coudyle of the femur, within the external 



