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



rib. Gervais and Alix found the muscle in Eudyptes clirysolophus arising from the 

 transverse process of the last cervical vertebra, as well as from the outer surfaces of the 

 first, second, third, and fourth ribs. According to the last-named authors, the muscle 

 consists of five distinct fascicles. In no species of Penguin have I observed more than 

 four. 



{h) Muscles inserted into the Humerus. 

 1. Pectoralis major. 



Grand pectoral, Vicq d'Azyr, 1772, p. 623, No. 1. 



Grand pectoral, Cuvier, 1805, vol. i. p. 277, No. 1. 



Described by Merrem, p. 152, No. 1. 



Der grosse Brustmuskel, Wiedemann, Bd. ii. p. 82. 



Pectoralis major, Tiedemann, p. 305, No. 1. 



Pectoralis major, Heusinger, Bd. vii. p. 183, No. 1. 



Grand pectoral, Meckel, torn. vi. p. 34, No. 8. 



Der grosse Brustmuskel, Schoepss, p. 108, No. 15. 



Pectoralis major, Eeid, 1835, p. 140. 



Pectoralis major, Eolleston, 1868, p. 624. 



Pectoralis major et minor, Selenka, Bd. vL p. 121, Nos. 46 and 47. 



Grand p>ectoral, Gervais and Alix, 1878, p. 24. 



Attachments. — The pectoralis major is an extremely powerful muscle. It arises 

 from the outer surface of the clavicle below the shoulder joint, from the outer surface 

 of a strong aponeurosis attached to the clavicle, sternum, and coracoid bones, by means 

 of a linear origin from the whole length of the sternal keel, as well as from the fascia 

 which intervenes between the pectoralis major and medius, and by means of a special 

 bundle of fibres from the postero-external, osseo-cartilaginous angle of the breast-bone. 



The anterior fibres pass transversely outwards, the posterior outwards and forwards, 

 while the intermediate fibres pass outwards with various obliquities. The anterior 

 clavicular, and neighbouring aponeurotic fibres end on a special tendon, which is attached 

 to the whole length of the anterior or radial margin of the bones forming the wing. 

 This tendon, moreover, expands into an aponeurotic sheath, which covers both surfaces 

 of the wing, and conceals the various tendons, blood-vessels, and nerves met with in the 

 dissection of that organ. The remaining fibres forming the bulk of the muscle terminate 

 on a V-shaped tendon, which is inserted into a special linear depression on the inner 

 surface of the humerus, between the anterior margin and the head of that bone. 



Action. — The two portions of this muscle have different actions. The anterior fibres 

 when contracting will carry the wing forwards, to a right angle with the trunk, while the 

 posterior fibres by their contraction will carry the wing backwards to produce the eff'ective 

 stroke in swimming through the water. Moreover, by reason of their insertion into the 

 anterior margin of the humerus, they will bring about that rotation of the wing round 



