UPPER HALF OF RABBIT. 31 



a. Bifid upper lip concealing muffle. See p. 26, y, infra. 



b. Sterno-mastoid muscle, arising from the prolongation of the manubrium into the neck and in- 



serted into the mastoid. 



c. Greater pectoral muscle of left side, arising along nearly the entire length of the sternum from the 



manubrium anteriorly down nearly to the leaf-shaped cartilage ending it posteriorly. 

 c '. Part of the origin of this muscle on the right side reflected. 

 c". Pouch-like insertion of it into the humerus, the fibres from the lower part of the sternum forming 



the posterior, those from the upper the anterior portion of the pouch ; the former passing to the 



inner ; the latter to the outer tuberosity of the humerus, and the outwardly- looking pectoro- 



deltoid ridge. 



d. Smaller pectoral muscle arising from the outer side of the keel-shaped manubrium superficially to 



the upper fibres of the greater pectoral, inserted together with fibres of that muscle and of the 

 clavicular portion of the deltoid into the fascia covering the biceps, and reaching by tendon nearly 

 to the lower end of the humerus at d" . 



d'. Tendon of origin of smaller pectoral of right side cut short. 



d" . Tendon of insertion of smaller pectoral of same side. 



e. Third pectoral muscle, corresponding to the pe.ctoralis minor of anthropotomy, as being similarly 



innervated, but inserted not into the coracoid, but into the head of the humerus, and only by a 

 few fibres into the costo-coracoid membrane. 



f. Deltoid, a bicipital muscle, its anterior head, supplied by the circumflex nerve, arising from the 



outer end of the clavicle and the fibrous tissues external to that insertion covering the shoulder- 

 joint, and the posterior head arising from the apex of the acromion and the anterior edge of the 

 metacromial process of the scapula. The external tuberosity of the humerus appears in the 

 interval between the two muscular bellies. 



g. Origin of sterno-clavicular muscle, from the sternum down to the level of the sixth rib, from the 



cartilage of which it receives some fibres, at a deeper level than that of the origins of the three 

 pectorals, but superficially to the plane of the rectus thoracis and of the sterno-costal muscle, 

 which are seen between the origin of the sterno-clavicular muscle and the plexus of brachial 

 nerves to form, with the first rib, a triangle with its apex pointing downwards and inwards. 



g'. Insertion of the sterno-clavicular muscle into the clavicle. The under fibres pass under the 

 clavicle without being attached to it, to be inserted, together with fibres from the two muscles 

 next to be named, into the spine of the scapula and the fascia covering the supraspinatus. 



//. Upper sterno- scapular muscle, continuous at its origin from the manubrium stemi with the sterno- 

 clavicular muscle, which may therefore be considered a prolongation of this muscle. 



/. Lower sterno -scapular muscle, arising from cartilage of first rib, innervated from the same source 

 as the two muscles, g and h, last mentioned, partially inserted like the stemo-clavicular, g, into 

 the clavicle, but passing on with it and the upper stemo-scapular, h, to be inserted into the 

 spine of the scapula and the fascia covering the infraspinatus muscle posteriorly. 

 j. Prolongation of the three muscles just named onwards on the left side from beneath the clavicle 

 to the insertion just specified ; the three next to be named, k, m, and n, having been removed to 

 allow of this being seen. 



k. Cleido-mastoid muscle, arising from occipital bone externally to stemo-mastoid, b, and inserted 

 into the greater part of the length of the bony clavicle. It is the homologue of the cleido- 

 mastoid portion of the human sterno-cleido-mastoid, holding the same relation to the cervical 

 plexus. There is no sterno-maxillary as in the Horse, and in the Hyrax. 



m. Cleido-occipital muscle, arising from the basioccipital just externally to the acromio-basilar, 

 inserted into the outer end of the clavicle, and the head of the humerus, and becoming continuous 

 between these two bony attachments with the fibres of the anterior portion of the deltoid. 



. Acromio-basilar muscle of right side, arising from the basi-occipital and inserted into the meta- 

 cromial process of the scapula just anteriorly to the insertion of the anterior part of the trapezius. 

 In most of the lower mammals this muscle arises from the atlas ; in some from the axis also, 

 thus coming to represent the upper digitations of the levator anguli scapulae in Primates. In 

 Rodents and some Ungulata, ' by becoming amalgamated by longitudinal and lateral fusion with 

 the recti capitis it may be attached to the lateral or basilar process of the occipital bone.' This 

 is the muscle called ' levator claviculae ' by Wood, pp. 88 and 94, ' acromio-basilar ' by Vicq. 

 d'Azyr, and ' acromio-trachelien ' by Cuvier, in whose Le9ons d' Anatomic Comparee, i. p. 271, ed. 

 2 de , we find it thus spoken of : 'On le trouve dans tous les mammiferes, I'homme excepte, ce 



