MUSCLES CONNECTED WITH THE SHOULDER-JOINT. C>1] 



cartilaginous band which reached in the embryo from the acromion to the presternum) the 

 subclaviits of Man passes up to be inserted into the costal surface of the outer half of' the 

 clavicle. The relation held by this fascia to the muscle furnish < . as I shall hereafter 



strive to show, a most important means for differentiating the pectorcUis minor of the 



Mammal from its siibchiriiis. The variations which the tubchtviut pr< tits in anthro- 

 potomy cast light, as such variations sometimes do, upon its homological representativ< 



in the lower animals. One of the most important of these variations is the junction to 

 the aubclavi s of another muscle, which, as arising ordinarily from the sternum, nia\ be 

 called a "sternoclavicular " muscle 1 , and may be thought, by virtue of this its point of 

 origin, to supply to the human subclavius the sternal factor which it r< quires to make if 



n co-extensive with that of an avian pectomlis wound t. Th prolongation of th< 



subclacii's to the acromion and scapula, so very common in quadruped mamma l s 

 is rare in the human subject, its fibres appearing to be, as it wei arrest 1 by the largely 



developed distal end of the clavicle. One instance of such an arrangement i^ Riven 



b 



_,. .... ..v ,~ ft 



as follows by Mr. Wood in the 'Proceedings of the Royal Society,' June 1866, p. 884. 



" In a thin female subject of low stature was found, on the ri ht side only, the remark- 

 able muscle riven in fii?. 4. It consisted of a roundish fusiform Blip (a), arising tendinous 



©** ~ » 



from the first cartilage below the subc/crius, close to the manubrium eterm, passing across 



the subclavian vessels and nerves, quit-- distinct from the last-named muscle, and in ted 

 into the upper border of the scapula and suprascapular ligament, where it was connected 

 to some extent, with the origin of the omo-hgoidetH (e). Prom this point of insertion 

 another slip of muscular fibres passed forwards, upwards, and outwards, to be inserted, 

 with the subclavius, into the outer third of the clavicle. 



a 



This muscle seems to be the same as that given in the author's first 



name of a double subclavius, with the addition of a connecting slip to the clavicle. It 

 seems to the author to represent pretty closely the » rnotcapular muscle, while contri- 

 buting to support the thorax in the Pachyderms and Ruminants, in which animals it is 



5? 



continued as far as the manubr 



It is singular that in the Crocodile some of the nbres of the omohyoid are, in youm 

 specimens at least, continuous with fibres of the epiooroAHhhumeral ; and it is obvious that 

 if, in the case just quoted from Mr. Wood's paper, the fibre- thus continuous with the 

 omohyoid had been prolonged a little, so as to become continuous with those of the deltoid 

 or supraspinatus, we should have had here a muscle corresponding both in origin and in 

 insertion very closely with the pectomlis aecundu* s. h Httor humeri of the bird. 



Now, as the following account of a dissection from the Gumeapig will show, just such 



a muscle exists in that animal : 



In the Guineapig (Cavia apeHa) the gubclaoius muscle, the smaller « >ternosca]>ular 

 of Mivart and Murie (Proc. Zool. Soc. June I860, p. 398) arises from a small surface I 



Kandrm Uvcaphva (ZooL Gart. April 1867, p. 128), of a very tine but strong elastic 1 1, which ran along the 



upper or anterior border of thej»*W« mi.or from the coracoid to the anterior end of the second rib, as Wing tl 

 homolo<me probably of the coracoid of 11 lotremes, Kids, and Reptiles. 



nomoio c ue pxuuau j 



thi 



June 1866, p. 238 ; Macalistcr, Proc. lioy. Irish Acad. Dec. 1867. 



