CONNECTED WITH THE SHOULDER- JOINT. 115 



junction to the subclavius of another muscle, which, as arising 

 ordinarily from the sternum, may be called a { sternoclavicular ? 

 muscle \ and may be thought, by virtue of this its point of origin, 

 to supply to the human subclavius the sternal factor which it 

 requires to make its origin co-extensive with that of an avian pec- 

 toralis secundus. The prolongation of the subclavius to the 

 acromion and scapula, so very common in quadruped mammals, is 

 rare in the human subject, its fibres appearing to be, as it were, 

 arrested by the largely developed distal end of the clavicle. One 

 instance of such an arrangement is given as follows by Mr. Wood 

 in the 'Proceedings of the Eoyal Society, 5 June 1865, p. 384: — 



'In a thin female subject of low stature was found, on the right side only, the 

 remarkable muscle given in fig. 4. It consisted of a roundish fusiform slip (a), arising 

 tendinous from the first cartilage below the subclavius, close to the manubrium sterni, 

 passing across the subclavian vessels and nerves, quite distinct from the last-named 

 muscle, and inserted into the upper border of the scapula and suprascapular ligament, 

 where it was connected, to some extent, with the origin of the omo-hyoideus (e). From 

 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. 



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

 the 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 sternoscapular muscle, while 

 contributing to support the thorax in the Pachyderms and Ruminants, in which 

 animals it is continued as far as the manubrium.' 



It is singular that in the crocodile some of the fibres of the 

 omohyoid are, in young specimens at least, continuous with fibres 

 of the epicoraco-humeral ; and it is obvious that if, in the case 

 just quoted from Mr. Wood's paper, the fibres 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 in- 

 sertion very closely with the pectoralis secundus s. levator humeri 

 of the bird. 



Now, as the following account of a dissection from the guinea-pig 

 will show, just such a muscle exists in that animal : — 



In the guinea-pig (Cavia aperia) the subclavius muscle, the smaller 

 ' sternoscapular ' of Mivart and Murie ('Proc. Zool. Soc.' June 1866, 

 p. 398), arises from a small surface on the praesternal proosteon and 

 from the cartilage of the first rib, exteriorly to which latter point 



1 For instances of this * second subclavius ' see Wood, ' Proc. Roy. Soc.' June 1864, 

 p. 300, June 1865, p. 384, and June 1866, p. 238 ; Macalister, « Proc. Roy. Irish Acad. 

 Dec. 1867. 



I 7, 



