CONNECTED WITH THE SHOULDER- JOINT. 139 



the homologue of the subclavius of other mammals. The prolongation of the 

 tendon of this muscular fascicle (ei) may be considered to be due to the with- 

 drawal of the Crocodile's epicoraco-humeral to the upper end of the coracoid. 

 Finally, as the rectus is often fused with the pectoral, we may regard this fascicle 

 as a nascent pectoralis minor. 



e o. Muscular fascicle arising from the tip of the freely ending cartilage of the first 

 thoracic rib (a point homologous with the points of origin of the several fascicles 

 of the external oblique), and passing downwards and forwards to end in an 

 aponeurosis attached mesially to the sternum and continuous with that of the 

 external oblique. By contracting a close adhesion to the fibres of the anterior 

 prolongation of the rectus abdominis instead of passing freely over them, as here, 

 this muscular slip may, in other animals, as e. g. Cynocephalus hamadryas, assume 

 the appearance of an outer head to this anterior prolongation. But its true 

 character of homology with the fascicles of the external oblique is seen as plainly 

 in the Guinea-pig {Cavia aperia) and the Aardvark (Orycteropus capensis), and, 

 according to Meckel (' Vergleich. Anatomie,' p. 454), in the Raccoon (Procyon 

 lotor) and in the Hedgehog (Erinaceus europceus), as it is here. In the Wombat 

 (Pkascolomys wombat) the true relations of this fascicle are very clearly seen ; 

 and a fascicle, obviously homologous with the one lettered e i in the Crocodile, 

 passes from under it to join the subclavius arising from the first rib. This latter 

 muscle arises, thick and fleshy, from the first rib in the Wombat, and is inserted 

 into the outer end of the clavicle, and, by means of the fascia covering the supra- 

 spinatus muscle, into the whole length of the spine of the scapula. Before its 

 insertion it is joined by a fine tendon from a delicate muscular belly, arising from 

 the sixth costal cartilage, and homologous with the muscular fasciculus figured 

 here at e i. Over this fascicle, which might be described in the Wombat as a 

 second head of the subclavius, there passes inwards from the outer part of the 

 first rib a muscular fasciculus, homologous with the one here figured in the 

 Crocodile as eo, to end in a broad tendinous aponeurosis over the sternum, 

 opposite the third and fourth costal cartilages. It is probable, on the whole, 

 that this fascicle eo may be really the homologue of the muscular slip which 

 is called 'rectus thoracis' by Professor Turner, I.e., and which, as figured and 

 described by him, appears to have a tendency to be produced obliquely inwards 

 towards the sternum. (See 'Journal of Anatomy and Physiology,' May 1868, 

 PP- 39 3> 394> ibique citata.) 



scl. Subclavius or triangularis sterni muscle, the ' pectoralis secundus ' of Haughton, 

 and ' costocoracoid ' of Mivart (' Proc. Zool. Soc' June 1867, p. 776). Its super- 

 ficial layer arises from the free cartilage of the second thoracic rib, and from the 

 intermediate and sternal elements of the third and fourth thoracic ribs, and is 

 inserted along the posterior edge of the coracoid. This muscle is obviously 

 homologous with the similarly stratified muscle of similar origin and insertion in 

 the bird, which is ordinarily called 'subclavius,' e.g. by Schoepss (Meckel's 

 Archiv, 1829); Du * & cannot be homologous with the pectoralis secundus or 

 levator humeri of the bird, inasmuch as the two muscles coexist with each other 

 there. The same reasoning shows that it is not homologous with a pectoralis 

 minor, though the slip which, in Alligator lucius, it gives to the muscle e i may 

 be so in part. 



cb. Coraco-brachialis, arising from anterior four-fifths of humeral edge of coracoid. 



be. Tendon of biceps, passing to be inserted on cephalic edge of coracoid. 

 Fig. 4. Muscles in connexion with the scapulo -coracoid arch and upper extremity of 

 the Emu, Dromaius novae hollandiae. 



p m. Pectoralis major. This muscle has a few fibres of origin in an aponeurosis 



