THE MUSCLES OF THE LOWER EXTREMITY. 249 



in a firm sheath of connective tissue, which masks at 

 first sight the individuality of the several muscles. 



For a centimetre or more above the tibial condyles 

 we observe their numerous tendons, as they start from 

 the lower apices of these different muscles ; while in the 

 division of the limb next below, we find the flexors at 

 the posterior aspect of the tarso-metatarsal shaft snugly 

 wrapped in fascia, and bound to the bone as a sub- 

 cylindrical bundle of tendons, the several factors of 

 which enjoy perfect freedom of action in the longitudinal 

 direction. The extensor tendons and the short extensor 

 muscle and other elements are somewhat differently 

 circumstanced in front in the very nature of their re- 

 quirements, but here, too, a fascia surrounds them in 

 a similar fashion, drawing them up snugly by the shaft 

 of the bone. 1 



1 In the second volume of his Anatomy of Vertebrates, Professor 

 Owen describes for the Apteryx (p. 104) a popliteus muscle, and says 

 it " is brought into view when the superficial muscles of the leg 

 which are inserted into the foot are removed. Its carneous fibres 

 extend from the fibula inward and downward to the tibia. It is of 

 relatively smaller extent than in the Cassowary." Professor Mivart 

 also alludes to the occurrence of this muscle in birds in his Elementary 

 Anatomy, but I must confess that after careful search in a number 

 of individuals, 1 have signally failed to find the popliteus in the 

 Raven. And I am rather inclined to believe that it will be found 

 to be absent in the higher groups of birds. It is present in the 

 Echidna. 



Since writing the foregoing paragraph of this footnote, I find 

 the following remarks and synonymy in Gadow on the popliteus 

 muscle in birds (foe. cit., pp. 176, 177). He does not mention it as 

 occurring in the Corvidce. 



" 44. M. POPLITEUS. 



Le muscle poplite. Yicq d'Azyr, p. 514. 

 Poplitieus. Wiedemann, p. 99. 

 Popliteus. Tiedemann, 303. 



