398 MR. ST. GEORGE MIVART AND DR. J. MURIE [Julie 2G, 



que ces muscles allant a l'humerus, ne represented pas le petit pec- 

 toral mais settlement certaines parties du grand pectoral, dans ce cas, 

 ma maniere de voir serait encore plus exacte." 



This muscle, however, seems distinct in the Rabbit, Hare, and 

 Guinea-pig, where it is seen as an elongated band, with an origin 

 adherent to and intermediate between the first portion and the sterno- 

 scapular. Its insertion, however, is quite separate, namely into the 

 ulnar tuberosity of the humerus, fibres also proceeding to the sub- 

 scapularis. 



Sterno-scapular. This muscle has a double origin. The larger 

 portion arises from the sternum, between the origins of the first and 

 second portions of the pectoralis major, and is closely invested by 

 them as before stated. As it passes upwards it becomes slightly 

 connected with the distal end of the clavicle, about an inch beyond 

 which it unites with the second and smaller portion of muscle, being 

 inserted together with it close to the anterior vertebral angle of the 

 scapula. Some fibres pass over the supraspinatus, and are attached 

 by fascia to the spine of the scapula. 



The second and rather smaller portion arises from the outer side 

 of the base of the manubrium and from the cartilage of the first rib. 

 Passing forwards it joins the first portion as already mentioned 

 (figs. 2 & 3, S.s.). 



The sterno-scapular is an exceedingly long aud narrow muscle. 

 The second, smaller portion resembles by its origin, and indeed may 

 be, the subclavius, as Meckel* suggests ; but it is the larger, and not 

 the smaller part which is unmistakeably connected with the outer 

 end of the clavicle, the lesser part having only an aponeurotic attach- 

 ment to that bone. 



In the Hare there is but one, broad origin to this muscle, a small 

 portion of its outer edge adhering firmly to the humeral extremity 

 of the rudimentary clavicle as it passes beneath ; while its insertion 

 is very extensive, viz. from the vertebral angle of the scapula to the 

 coracoid process, upon the surface of the supraspinatus. In the 

 Rabbit and Guinea-pig there are two slips as in D. cristata. 



The deltoid consists of two semidistinct portions — one arising from 

 the inferior border of the metacromion process (tendinous superfi- 

 cially), the other investing the fascia of the infraspinatus immediately 

 behind that process. These two portions have a common insertion 

 into the lower half of the deltoid ridge, immediately external to the 

 summit of insertion of the second part of the pectoralis major 

 (fig. 3, D.). 



This corresponds with our dissection of the same muscle in the 

 Rabbit, Guinea-pig, and the Hare. 



Meckel f considers the deltoid in the Agouti and Porcupine to 

 consist of a clavicular as well as a scapular portion ; but what he 

 describes as the former is our fourth portion of the pectoralis major. 



This may indeed be described as part of the deltoid ; but, on ac- 

 count of its very different insertion from that of the ordinary clavi- 

 cular part of the deltoid and its insertion in common with the third 

 * Loc. tit. pp. 259, 260. t Loc. tit. p. 255. 





