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



Variations. — The insertion of the combined cruro-coccygeus and adductor longus 

 varies somewhat in diflFerent species. In Spheniscus clemersus and Spheniscus magellani- 

 cus their insertion is confined to the middle third of the shaft of the femur ; in Eudyiotes 

 chrysolophus they are attached to the lower third of that bone ; whilst in Aptenodytes 

 their insertion occupies the lower two-thirds of the shaft of the femur. 



Remarks. — There is some difficulty with regard to the synonymy of this as well as 

 of the preceding muscle. Both are described by Selenka under the name of adductor 

 longus. According to this author, the muscle in some birds arises exclusively from the 

 coccygeal vertebrae, while in others its origin is confined to the pelvis. In the former 

 the muscle evidently corresponds to the cruro-coccygeus above described, while in the 

 latter it represents my adductor longus. Selenka does not refer to the presence in any 

 one bird of both the pelvic and coccygeal origins of his adductor longus, and yet this 

 occurs in every species of Penguin which I have examined. 



5. Adductor magniis. 



Le deuxikme dbducteur de la cuisse, Vicq d'Azyr, 1774, p. 508, No. 3. 



Uer zweite Anzieher des Oherschenkels, Wiedemann, p. 97. 



Der zweite Anzieher des Ohersehenkelheins, Tiedemann, p. 329, No. 7. 



Addudeurs (one of), Cn^der, vol. i. p. 359. 



Muscle No. 9, I\Ieckel, vol. vi. p. 86, No. 9. 



Triceps adductor femoris (part of), Eeid, p. 143. 



Adductor magnus, Owen, p. 35. 



Adductor magnus, Selenka, vol. vi. p. 141, No. 80. 



Adducteurs (one of), Gervais and Alix, p. 31. 



Attachments. — The adductor magnus is a very powerful muscle. It arises from the 

 whole length of the outer surface of the pubic bone, posterior to the acetabulum, as 

 well as from its posterior cartilaginous extremity, and to a corresponding extent 

 from the outer surface of the obturator membrane. The fibres pass obliquely downwards 

 and forwards, and are inserted into the lower half of the posterior border (linea aspera) of 

 the shaft of the femur. A few of the posterior fibres are inserted by means of a special 

 tendon into a depression on the posterior .surface of the femur, immediately above the 

 internal condyle of that bone. To this tendon are attached a few of the fibres of the 

 inner head of the gastrocnemius. 



Action. — This muscle is a powerful extensor of the femur at the hip joint. Through its 

 connection with the gastrocnemius it flexes the knee and extends the ankle joint. 



Relations. — At its origin the muscle corre.sponds to the lower border of the obturator 

 externus. On the outer side it is in contact with the adductor longus and cruro- 

 coccygeus. Its posterior border lies parallel to, and in contact with the pubic head of 

 origin of the semi-membranosus. 



