322 SHOULDER-GIRDLE IN MONOTREMES 



posterior surface of the humerus; while {d) distal internal humeral 

 head arises from the distal half of the posterior surface. 



Insertion. Both portions of the muscle are inserted on 

 the anterior border of the summit (dorsal surface) of the olecranon. 

 A bundle of fibres differentiated, from the inner border of the 

 "proximal internal portion of the muscle" (cj is inserted separately 

 at the inner extremity of the olecranon. 



Innervation. N. musculo-spiral. 



Westling — Echidna : branch from N. radialis profundus. 



Echidna. 



Westling describes the triceps as arising from (1) the glenoid 

 border of the scapula ; (2) from the humerus in two layers, the 

 superficial from the proximal part, the deeper from the distal part 

 of the humerus; (3) a narrow portion associated with the super- 

 ficial (of 2) and arising by a tendon just distal to the articular 

 head of the humerus. Westling then goes on to say, " zwischen 

 diesem Zipfel [3] und dem iibrigen Theil der oberflachlichen 

 Schichte gehen die Arteria brachialis und ein Ast des N. radialis 

 superficialis hindurch. Der Ursprung der tiefern Schichte streckt 

 sich weit distalwarts, wodurch deren distalen Fasern eine voUig 

 horizontale Richtung erhalten und parallel mitdem M. epitrochleo- 

 anconeus (M. antanconeus, Coues) werden, nur durchdie Nn. ulnaris 

 und medianus von diesem Muskel getrennt. Sowohl der scapulare 

 wie der humerale Tlieile inseriren fleischig an der ganzen Breite 

 des Olecranon." 



Leche follows Westling. 



MiVAET describes the origin from the glenoid border of the 

 scapula, and says that this portion is inserted by muscular fibres 

 on to the whole breadth of the olecranon. "The humeral portion 

 covers the entire posterior surface of the shaft of the humerus, 

 whence alone it takes its origin, with the exception of a small and 

 more or less distinct slip, which arises by a marked tendon 

 from beneath the posterior part of the greater tuberosity immedi- 

 ately external to the origin of the supinator longus. It is inserted 



