J. Plavfair McMurrich 



43 



possibilities is the easier of accomplishment; it is not a migration, but 

 the formation of a new attachment in the course of the muscle and the 

 degeneration of the part above. And, as already noted, there is evidence 

 of the occurrence of such a process in at least one of the muscles found 

 in man. On this view the tibial superficial muscle of the lacertilian 

 crus is to be regarded as having in reality a femoral origin and agrees 

 in its primary relations with the other superficial muscles. 



Traced downwards the plantaris superficialis medialis becomes a 

 broad band which inserts into the tibial border of an aponeurotic sheet 

 (Fig. 4, a) which represents a portion of the superficial layer of the 

 plantar aponeurosis and receives also the insertion of the plantaris super- 

 ficialis lateralis. 



Fig. 4. — Transverse section through the lower part of the crus of Scincus «p. 

 a, superficial portion of plantar aponeurosis; o'.deep portion of plantar aponeuroals ; 

 f, ramus superficialis flbularis ; F, fibula ; fc, fibular cutaneous nerve ; I, interosseus ; 

 /', vertical fibers of interosseus : p, ramus profundus ; pc, cutaneous branch of ramus 

 profundus ; Pp-/.plantaris profundus I : PijII-jII/, plantaris profundus II-III ; PsJ,plantaris 

 superficialis lateralis ; Psm, plantaris superficialis medialis ; T, tibia. 



The plantans superficialis tenuis (Fig. 3, Pst) takes its origin above 

 the knee joint from a sesamoid cartilage developed in a tendon arising 

 from the fibular border of the flexor tibialis externus (Gadow) and 

 passes downwards to unite with the tibial border of a portion of the 

 plantar aponeurosis which covers tlie posterior surface of the plantaris 

 profundus II-III (Fig. 4, a'). The muscle is slender throughout its 

 entire course. At first it lies superficially between the medial and lateral 

 superficial plantars, but lower down it is covered by the fibular edge of 

 the medialis and at about the middle of the crus fuses with the posterior 

 surface of the deep plantar mass, or, as it is better expressed above, 

 inserts into the tibial border of a portion of the plantar aponeurosis which 

 covers the deep plantar mass. 



This muscle does not seem to be present in all lacertilia. Thus Perrin, 

 93, fails to find it in Uromastix and I have not succeeded in observing 



