112 THE VOYAGE OF H.M.S. CHALLENGEE. 



femoris (the tensor fasciae above described) is absent in the Penguins. I have found it 

 in every species, although reduced to a minimum in size. 



4. Biceps femoris. 



Muscle No. 2, Vicq d'Azyr, 1774, p. 506, No. 2. 



Biceps, Cuvier, voL i. p. 371. 



Der ziigespitzte Wadenbein-iluskel, Merrem. 



Der vordere Beiiger des Unterschenkds, Wiedemann, p. 96. 



Der erste Beuger des Unterschenhds, Tiedemann, p. 334, No. 6. 



FUehisseur peroneal, ^Meckel, voL vi. p. 90, Xo. 3. 



Gluteus jnaximus, Eeid, p. 143. 



Biceps flexor cruris, Owen, p. 36. 



Biceps, Solcnka, voL vi. p. 143, No. 86. 



Biceps femoral, Gervais and Alix, p. 32. 



Attachments. — The biceps is a very powerful muscle, which arises from the whole 

 length of the upper (dorsal) border of the ilium and ischiimi extending fi-om the acetabulum 

 backwards to the posterior extremity of the pelvis, as also by means of a separate bundle 

 of fibres from the posterior border of the tendon of origin of the tensor fasciae femoris. 

 The muscular fibres end above the knee joint on a rounded tendon, which, after passing 

 through a fibrous pulley bned by syno"sdal membrane, is inserted into a well-marked 

 tubercle, situated on the outer side of the fibula, at the junction of the upper and middle 

 thu'ds of that bone. The tendon through which the tendon of this muscle passes consists 

 of a fibrous loop, which is attached by its upper end to the outer side of the shaft of 

 the femur, immediately above the outer condyle, whilst its lower end coalesces with the 

 tendinous outer head of orio;tn of the gastrocnemius muscle. 



Action. — This muscle is the most powerful of the flexors of the knee joint. Indirectly 

 it extends the femur at the hip joint. 



Relations. — The muscle is superficially placed except at its insertion where its tendon 

 intervenes between the outer head of origin of the gastrocnemius on the outer, and the 

 flexor sublimis digitorum on the inner side. Its deeper surface rests upon the sciatic 

 nerve which separates it from the semi-tendinosus muscle. Its anterior border lies parallel 

 to and in contact with the posterior border of the tensor fascitB. 



]\^erve supply. — Several branches of the sciatic nerve, which are given ofi" directly after 

 the latter has escaped from the pelvis. They enter the deeper surface of the muscle. 



Remarks. — Tiedemann, followed by Selenka, identifies the muscle above described 

 under the name of biceps, with the biceps of Yicq d'Azyr. A careful reading of the 

 description of the last named author, shows that the biceps of Tiedemann and Selenka is 

 the " demi-membraneux " of Yicq d'Azyr. 



