90 THE VOYAGE OV H.M.S. CHALLENGER. 



observed by any other anatomist who has investigated the anatomy of the 

 Spheniscidse. 



(c) Muscles inserted ikto the Radius and Ulna. 



1. Triceps extensor cuhiti. 



Le grand extensnir du coude, Vicq d'Azyr, 1773, p. 571, No. 1. 

 Extenseur de I'avant bras, Cuvier, vol. i. p. 296. 

 Described by Merrem, p. 15.5, Nos. 1 and 2. 



Der laiige dusaere tend innere EUenhogenmuskel, Wiedemann, pp. 86 and 89. 

 Anconeug lonffus et hrevis, Tiedemann, p. 314, Nos. 7 and 8, and p. 315, No. 9. 

 Der lange, kurzere, und Meinste Ellenhogenknorrenmuskel, Heusiuger, p. 185, Nos. 16, 17, 18. 

 L'extenseur de I'avant bras, Meckel, vol. vi. p. 53, No. 9. 

 Der Streckm- des Vorderarines, Schoepss, p. 130, No. 23. 

 Triceps extensor ciibiti, and anconeits, Eeid, p. 142. 

 Triceps brachii, Selenka, vol. vi. p. 126, No. 53. 



La longue portion du triceps brachial, le vaste externe, et le vaste interne, Gervais and Ali.x, pp. 

 25 and 26. 



Attachments. — This, the great extensor of the forearm, consists of four distinct heads. 

 The first and largest head arises from the inner or thoracic surface of the dorsal recurved 

 extremity of the clavicle immediately behind the origin of the tensor patagii longus, to 

 a small extent from the coraco-clavicular ligament, and from the acromion process of the 

 scapula. The muscular fibres composing this head form a triangular belly, which arches 

 downwards and outwards to terminate on the tendon common to this and to the second 

 head. The second head arises from the axillary border of the scapula, immediately 

 behind the glenoid fossa, close to the attachment of the fibrous pulley through which 

 pass the tendons of the latissimus dorsi. The third head arises from the trieijMtal fossa 

 of the humerus, whUe the fourth head is attached to the whole length of the posterior 

 or ulnar border of the humerus. The first and second heads unite together immediately 

 behind the shoulder joint, the common tendon being subsequently joined by the 

 muscular fibres of the third head. Thereafter the tendon of insertion divides into two 

 parts — an inner and an outer. The inner tendon receives the majority of the muscular 

 fibres which form the fourth head of origin, and after passing behind the elbow joint is 

 inserted into an angular projection on the upper end of the posterior margin of the ulna. 

 In connection with this tendon, as it passes over the elbow joint, is developed the inner or 

 smaller of the two ulnar sesamoid- bones. The outer tendon of insertion of the triceps 

 receives a few of the muscular fibres which form the fourth head of the muscle, and passing 

 behind the elbow joint is inserted into the outer side of the upper end of the ulna, 

 midway between the insertion of the inner tendon and the articular surface for the recep- 

 tion of the humerus. In connection with this tendon is developed the outer or larger 

 of the two ulnar sesamoid bones. 



