116 THE VOYAGE OF H.M.S. CHALLENGER. 



minimus, and downwards to the femoral condyles. That portion of the common muscular 

 mass which arises from the anterior surface of the femur (crureus) is the stronger, and is 

 inserted into the upper truncated extremity of the patella, while the muscular fibres 

 which arise from the outer surface of the femur (vastus externus) are inserted, for the most 

 part, by means of a flattened tendon into the outer surface of the patella, and to a small 

 extent into the upper end of the external anterior tibial crest. The two portions of the 

 muscle, however, both at their origin and insertion, are quite continuous with one another. 



Relations. — The muscle lies between the insertion of the adductor magnus on its outer, 

 and the origin of the gracilis on its inner side. The tendon of insertion common to the 

 tensor fasciae femoris and rectus femoris is inseparably united with the extensor 

 cruris, opposite the middle in length of the femur. 



Action. — This muscle is the principal extensor of the knee joint. 



Nerve supply. — The crural nerve gives off several twigs which enter this muscle. 



Remarks. — Gervais and Alix describe the two portions of the extensor cruris as 

 distinct muscles in Eudyptes chrysolophus. 



9. Popliteus. 



Le muscle poplite, Vicq d'Azyr, 1774, p. 514, No. 5. 

 Le nniscle popliU, Meckel, vol. vi. p. 98, No. 9. 

 Der Knlrkehlen-MiisM, Tiedemann, p. 336, No. 10. 

 Popliteus, Owen, p. 37. 

 Le jwplite, Gervais and Alix, p. 33. 



Attachments. — The popliteus arises immetliately below the knee joint, from about half 

 an inch in length of tlie postero-internal border of the tibia, as well as from a corres- 

 ponding extent of the posterior surface of that bone. The fibres pass obliquely u^iwards 

 and outwards, and are inserted into the posterior border of the upper end of the fibula. 



Action. — This muscle approximates the posterior border of the fibula to the tibia, by 

 rotating the former round the axis of the shaft of the bone. This movement is coincident 

 with rotation inwards of the tibia upon the lower end of the femur. 



Relations. — The origin of the muscle lies to the outer side, and in contact with that 

 of the plantaris. It is concealed by the flexor perforatus digitorum. 



Nerve supply. — A branch from the sciatic nerve. 



(c) Muscles I^^SERTED into the Tarso-Metataesus. 



1. Gastrocnemius. 



Les jumeaux, Vicq dAzyr, 1774, p. 511, No. 1. 

 Der Wadenmuskel, "Wiedemann, p. 101. 

 Der i/rosse Waderimuslcel, Merrem. 

 Der Wadenmuskel, Tiedemann, p. 336, No. 1. 



