We remember that the transverse processes are often, from their relation with the trachea, known as the tracheal processes. Hence the word ‘trachelian,’ which forms part of the name of the muscle with which we are now dealing.
By its contraction it helps to draw the anterior limb forwards.
When this muscle, as an abnormality, exists in man, it arises from the clavicle or the acromion process, traverses the supraclavicular fossa, and is inserted into the transverse processes of the atlas or axis, or of both these vertebræ, or of the cervical vertebræ below these latter. It is then known by the names of the elevator of the clavicle or elevator of the scapula, and, finally, as the cleido-omo-transversalis (Testut).[23]
[23] L. Testut, ‘Les anomalies musculaires chez l’homme expliquées par l’anatomie comparée,’ Paris, 1884, p. 97. A. F. Le Double, ‘Traité des variations du système musculaire de l’homme et de leur signification au point de vue de l’anthropologie zoologique,’ Paris, 1897, t. i., p. 235.
The Levator Anguli Scapulæ ([Fig. 68], 15; [Fig. 70], 23).—As we have pointed out (p. 136), the levator anguli scapulæ, because of its connections with the great serratus, is sometimes described with it. But inasmuch as in human anatomy these two muscles are considered separately, and that, in the superficial layer of muscles, they are seen in different regions—the great serratus in the thoracic, and the levator anguli scapulæ in the cervical—we prefer to study them separately.
We remember that in man this muscle arises from the transverse processes of the upper cervical vertebræ and is inserted into the superior portion of the spinal border of the scapula, into the portion of this border which is situated above the spine; it also contributes to the formation of the floor of the supraclavicular region.
When it contracts, it draws the superior portion of the scapula forwards and upwards, and causes a see-saw movement, for at the same time the inferior angle of the scapula is directed backwards. Taking its fixed point at the shoulder, it directly extends the neck if the muscle of one side acts at the same time as that of the opposite; but if only one muscle contracts it inclines the neck to the corresponding side.
It is to be noticed that during movements a little more active than the ordinary the levator anguli scapulæ, as moreover the other muscles of the neck do, becomes very distinct. We have, indeed, often remarked that, apart from these movements, each time the support of one of the fore-limbs is brought into requisition a brusque contraction of the muscles of this region accompanies it.
This contraction gives the impression that, as on the one hand, each support determines a momentary arrest of progression, a jolt, and on the other hand, the head continues to be projected in the forward direction, the latter should be retained. But it cannot be so except by an effort in the opposite direction—that is to say, by the brusque contraction which we have just pointed out.
Analogous contractions also take place in a man while running at the beginning of each contact of the lower limbs with the ground.