MUSCLES CONNECTED WITH THE SHOULDER-JOINT. 



61.* 



muscular fasciculi as its mbclavim; what I do affirm is, that there is a certain landmark 

 between these two muscles enabling us to Beparate them into two set-, and that there is 

 a similar separation recognizable in the bird, of similar muscles bv means of a similar 

 landmark. Under the second head I shall shim thai the subclavian of the mammal 

 supplied by a nerve homologous with the nerve which supplies the per/ora/is m ciwdwt of 

 the bird, and that the pectoralis minor is nol supplied by that nerve, but by the sami 

 nerve as that which in the bird supplies the great pectoral. And. thirdly, I shall show 

 that in the developing bird it is possible to see that the pectoralis major is really the 

 equivalent of both pectorals of the mammal ■ The facts of the anatomical arrangements 

 in any single bird will give my arguments in their most intelligible form; and I will 

 proceed to give them in an account of the structures in question, as M-cn in the common 

 Sparrow-Hawk {Accipiter Nisas). 



The pectoralis secuadns s. levator humeri has a much smaller area of origin from the 



sternum and its keel in the Bjuarow -Kdwk (Accipiter Affiant) than in the Common Fowl, 

 It receives, however, an accession of fibres, first from the anterior inferior angle of the 



coracoid, and secondly from a large head which, ari-ing from the posterior or upper 



surface of the coracoid groove in the sternum, from the lateral aspect of the sternal 



rostrum, from the upper surface of the inner angle of the coracoid itself, and, finally, 

 from the upper surface of a fibrous band which passes from the posterior lip of the cora- 

 coid groove in the sternum to fix itself to the posterior and inner edge of the coracoid at 

 about the middle of the height of the bone, may be considered the homologue of the 

 large " coraco-brachialis superior" of Gallinaceous birds*. A dense band of ligamentous 

 tissue (homologous probably with the prsecoracoid of the lizards) stretches in the 

 coraco-clavicular membrane from the sternal rostrum to the upper end of the clavicle; 

 and from it a thin sheet of muscular fibres arises, n hieh joins tin- tendon of the pectoralis 



dus in the pulley, as does also a slender slip of mused 



pass* - from 



mesoscapula. The main mass of the pectoralis seciitnlus is of a deeper colour, especi 



young birds, than 



latter muscles, which join its tendon ; and it is to be 



remarked that the main mass, as well as the former of these accessory slips, t 

 from the fibrous band in the coraco-clavicular ligament. 



A ligament passes from 



anter 



exterior auffle of the coracoid al its sternal 



culation (the "epicoracoid" of Parker) to be inserted on the sternum at a point about 

 opposite the articulation of the third sternal rib. It limits the fibres of the pectorah 

 secundvs mesially from those of the so-called " subclavius " (no. xi. of Schoepssf) ex- 

 inwards to attach them- 



ternally, at the point 



latter pass upwards and 



selves to the base of the coracoid. Inasm 



is the two lavers of the "sub 



clavius " of the bird are homologous serially with the two layers of the intercostals 

 ligament mav be considered homologous with the mesial attachment of the costo- 



* The lower part of this latter muscle is aborted as far as its ordinary dir< >n is concern. -d. its upper part being 

 represented by a very slender slip which arises from the posterior asp t of the mesocoracoid c ion « lose, to th 

 glenoid, and, taking the usual course of a coraco-brachialis, is inserted with th< -ui ipularis 



f « Beschreibung der Flugelmuskeln der Yugel. Von C. GL Schoeps " Meckel's Archiv, L8S», p. 72. 



VOL. XXVI. 



4 Q 



