Among the muscles which we have just enumerated are some that we have already studied; these are the sterno-prescapular and the rhomboid. We will examine the [supraspinatus] muscle in connection with the region of the shoulder.
As to the scaleni muscles and the complexus, they are deeply situated, whereas the omo-hyoid is visible in the anterior region of the neck only.
There remain for us, accordingly, to examine, at the present juncture, but the omo-trachelian, levator anguli scapulæ, and splenius muscles.
The Omo-trachelian Muscle ([Fig. 68], 13; [Fig. 69], 17; [Fig. 70], 20).—Also called the acromio-trachelian, levator ventri scapulæ,[21] the angulo-ventral muscle, and the transverso-scapular,[22] etc., this muscle is described by some hippotomists as belonging to the mastoido-humeral, of which it then forms its posterior or deep portion (see [p. 153]).
[21] Ventri, because inserted into the inferior part of the spine of the scapula, towards the acromion—that is, on the ventral side—by contrast with the trapezius, which is attached higher up (dorsal side) on the same process.
[22] Among the many names given to this muscle, Arloing and Lesbre recommend the adoption of the name ‘transverse scapular’ given by Straus-Durckheim, or ‘transverse of the shoulder’ (Arloing and Lesbre, ‘Suggestions for the Reform of Veterinarian Muscular Nomenclature,’ Lyons, 1898).
The omo-trachelian muscle is found in all mammalia, man alone excepted. It is, however, sometimes found in the human being; but it then constitutes an anomaly.
In the dog, pig, and ox, it arises from the inferior part of the spine of the scapula, in the region of the acromion, and terminates on the lateral portion of the atlas.
In the cat it is attached besides to the base of the occipital bone. It is visible in the space limited by the trapezius and the mastoido-humeral, the direction of which it crosses obliquely.
In the horse it appears to be blended in clearly defined fashion with the mastoido-humeral. Attached below, like this latter, to the anterior border of the humerus, it covers the scapulo-humeral angle; and is attached by its upper portion to the transverse processes of the first four cervical vertebræ.