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Show 398 MR. ST. GEORGE MIVART AND DR. J. M U R I E [June 26, que ces muscles allant a 1'humerus, ne representent pas le petit pectoral mais seulement certaines parties du grand pectoral, dans ce cas, m a manicre 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 subscapularis. 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 and 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 attachment 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 verv 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 superficially), 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. Meckelf 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 m a y indeed be described as part of the deltoid ; but, on account of its very different insertion from that of the ordinary clavicular part of the deltoid and its insertion in common with the third * Loc. cit. pp. 259, 260. t Loc. cit. p. 255. |
