BY W. J. S. McKAY 319 



TIlis origin shows the subscapularis accessorius to belong to the 

 the group of muscles that lie ventral to the glenoid ridge. But 

 when we examine the origin of the teres minor in Monotremes, 

 we find that it is placed between the infraspinatus and the long 

 liead of the triceps which arises from the glenoid ridge, that is to 

 say, that its origin is dorsal to the glenoid ridge, and therefore the 

 muscle can have no connection with the subscapular group of 

 muscles. 



As regards its insertion, an apparent objection arises, inasmuch 

 as the muscle, instead of being inserted on the posterior aspect of 

 the humerus close to the greater tuberosity, is inserted on the 

 posterior aspect of the humerus close to the lesser tuberosity. 

 But this unusual insertion is not so irregular when we consider 

 that the proximal end of the humerus is flattened and widened to 

 a very gi-eat extent, and the distance between the two tuberosities 

 is very considerable, and the insertion of this muscle stretches for 

 some distance over this space without, however, reaching the 

 greater tuberosity. Lastly, the muscle is supplied (in Echidna) 

 from two sources. The larger nerve of supply coming from the 

 cord common to it and the N. axillaris, whilst from the latter a 

 small branch is given off which runs to communicate with the 

 larger nerve above mentioned. Westling also mentions this 

 arrangement of the nerve supply in Echidna ; though we, our- 

 selves, did not find it in Ornithorhynclms ; there being no com- 

 munication in this form from the N. axillaris. The nerve supply, 

 therefore, in our opinion, though not conclusive, is strongly in 

 favour of our view that the muscle is really a teres minor. 



M. TRICEPS. 

 EcHiDXA et Ornithorhynchus : Trictpn, all authors. 

 Echidna. 



The triceps arises by four heads. 



Origin. («) Scapidar portion. — This arises from the ventral 

 half of the glenoid ridge, and from a ridge on the coracoid just 

 immediately posterior to the glenoid cavity. 



