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



ulnar metacarpal bone. It passes obliquely downwards and inwards, to be inserted into 

 the base of the ulnar phalanx. 



Action. — It flexes (adducts) the ulnar phalanx upon the corresponding metacarpal bone. 



Relations. — The outer side of the muscle rests against the flexor brevis metacarpi. 

 The dorsal interosseous muscle lies parallel to its radial border. 



Nerve supply (?) 



6. Abductor digiti secundi. 



Der Streclcer des erstcn Fingergliedes, Wiedemann, p. 94. 



Strecker des ersten Gliedes des zweifen Fingers, Tiedemann, p. 322, No. 4. 



Strecker des ersten Oliedes des zwciten Fingers, Heusinger, p. 193, No. 34. 



L'addudeur du deuxihme doigt, Meckel, vol. vi. p. 77, No. 8. 



Der Anzieher des Zeigefingers, Schoepss, p. 170, No. 45. 



Vierter intei-osseus, Seleuka, vol. vi. p. 137, No. 70. 



Vahdueteur du deuxihme doigt, Gervais and Alix, p. 29. 



Attachments. — This muscle is represented by a tendon which arises from the upper 

 half of a slio'lit groove, situated on the inner surface and close to the anterior marmn 

 of the radial metacarpal bone. It passes downwards, and is inserted into the inner side 

 of the base of the first radial phalanx. 



Relations. — It lies in the groove of the radial metacarpal bone, from which it arises. 



Variations. — In Aptenodytes longirostris, Pygosceles tcBuiatus, as well as in an 

 example of Eudyptes chrysocome from Tristan d'Acunha, this tendon was provided with 

 a distinct but weak muscular belly. In Pygosceles this muscle is traceable as far as 

 the base of the second radial phalanx. In all the other species examined the muscle 

 was entirely replaced by tendon. 



Remarks. — According to Schoepss and Meckel, this muscle is entirely wanting in 

 the Penguin. In Eudyptes chrysocome, Gervais and Alix, like myself, found it repre- 

 sented by tendon. 



7. Interosseus dorsalis. 



L'intcrosseux anterieur, Vicq d'Azyr, 1773, p. 577, No. 5. 



Der dussere Mittelhandmuskel, Tiedemann, p. 325, No. 10. 



Der dussere MittelhandmusTcel, Heusinger, p. 197, No. 39. 



L'extenseur et ahdiicteur interne du detixieme doigt, Meckel, vol. vi. p. 77, No. 6. 



Abzieher des Zeigefingers, Schoepss, p. 172, No. 46. 



Interosseus, Selenka, voL vi. p. 137, No. 69. 



Interosseux dorsal, Gervais and Alix, p. 30. 



Attachments. — The dorsal interosseous muscle is slender. It arises from the whole 

 length of the contiguous borders of the radial and ulnar metacarpal bones. The 

 muscular fibres end on a delicate tendon, which, after passing between the first radial 

 and ulnar phalanges, is inserted into the base of the last radial phalanx. 



