106 
PROFESSOR WOOD ON THE NECK- AND SHOULDER-MUSCLES. 
fibres of insertion of a broacl triangular muscular layer (Plate X. fig. 16, Z), arising from 
the sternum under the 'pectorals. This is clearly the homologue of the sterno- clavicular 
muscle, disguised by its connexion with the sterno-scapular. 
The group of muscles just described have been taken together as one to. pectoralis 
minor by Krause (op. cit. S. 104), and as the subclavius by Cuvier (Recueil, pi. 233), 
but the interposition of the clavicle between the upper and lower portions of the deeper 
layer points evidently to their correspondence, respectively, to the scapulo-clavicular and 
sterno-clavicular of other animals ; and they are, at least, as worthy of separation as the 
component parts of the cephalo-humeral , as distinguished by the same bone or its tendi- 
nous representative. Another portion of the pectorals of the Rabbit answer more closely 
than these to the pectomlis minor of Man. 
The sterno-scapular muscle in the Guinea-pig (Plate X. fig. 17, A & B, i) corresponds 
with a subclavius in being attached to the movable clavicle (x) by its more superficial 
fibres, while the deeper are continued to the outer part of the spinous process of the 
scapula, where it is inserted between the supraspinatus (q) and infraspinatus. In the 
same animal the scapulo-clavicular muscle (7c) is very considerable in size and distinct 
from the supraspinatus , over which it moves freely ; arising from the scapular spine and 
supraspinous fascia, internal to the last, and inserted into the movable clavicle (x) 
opposite to the sterno-clavicular (l). This last-named muscle arises from the middle of 
the sternum, between and partly covered by the upper and lower fibres of the pectorals, 
forming a triangular layer very distinct in its origin and insertion. In the Norway Rat 
(Plate X. fig. 19, & Plate XI. fig. 26) the subclavius proper (to) is represented by a small 
bundle of fibres arising to the inner side of the sterno-scapular , and inserted into the lower 
surface of the inner end of the clavicle (x). The sterno-scapular is a fusiform muscle 
(i) ending in two tendons of insertion, one with the omo-hyoid into the cervical border, 
and the other into the acromion process of the scapula. The scapulo-clavicular (7c) in 
the same animal is very distinct, arising from the middle of the supraspinous fascia, and 
inserted into the outer end of the clavicle (x). This bone articulates directly both with 
the sternum and scapula, so that the action of the muscle upon it presents nearly the 
same conditions as in the human subject, and is necessarily more limited than in the 
Rabbit and other semiclaviculate animals. 
The sterno-scapular muscle has been described by Murie and Mivart in the Hyrax 
capensis as arising from the sternum in front of the origin of the pectorcdis minor , and 
continued over the shoulder articulation to its insertion into the anterior superior 
angle of the scapula (op. cit. p. 338). They also found it in the Guinea pig, together 
with a slip from the supraspinatus to the clavicle ( scapulo-clavicular ), and state that 
Meckel describes it as a part of the subclavius in the Hare, Porcupine, and Agouti 
(pp. 259, 260), and that Cuvier considered it as part of the trapezius ? (Lemons, vol. i. 
p. 373). In the ‘ Recueil de Planches ’ it is marked in the Rabbit as subclavius (pi. 233). 
In the Crested Agouti, Mivart and Murie found the sterno-scapular to have a double 
origin, viz. a larger, from the sternum between the pectoral bundles ; and a smaller, from 
