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.
h. Upper sterno-scapular muscle, continuous at its origin from the manubrium sterni with the sternoclavicular muscle, which may therefore be considered a prolongation of this muscle.
i. 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 sterno-clavicular, g, into the clavicle, but passing on with it and the upper sterno-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.
n. Acromio-basilar muscle of right side, arising from the basi-occipital and inserted into the metacromial 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 Lecons d'Anatomie Comparee, i. p. 271, ed. 2de, we find it thus spoken of: 'On le trouve dans tous les mammiferes, l'homme excepte, ce qui semblerait prouver qu'ils est une des conditions de la station quadrupede.' This would apply more correctly to the prolongation of the muscles, g, h, z, on to the scapula, as shown on the left side at j.
n'. Metacromial insertions of acromio-basilar and trapezius.
o. Anterior or cervical portion of serralus magnus of left side, exposed by the removal of the three last-named muscles. A muscular fascicle, which not rarely arises between the upper part of the origin, here seen, of the serratus and those of the scaleni, is not shown in this figure. It is a long and slender slip, and passes down vertically to join the thoracic portion of the serratus, and to be inserted with it into the posterior and inferior angles of the scapula, and appears, when compared with the omohyoid of the horse, to represent that muscle.
p. Sterno-hyoid muscle, arising from sternum and cartilage of first rib.
q. Sterno-thyroid, fused posteriorly with dorsal surface of preceding muscle.
s. Stylo-hyoid, with its tendon running along the thyro-hyal portion of the hyoid arch at an oblique angle to its muscular belly. Within this angle lies the ninth nerve. The trunks and branches of the pneumogastric and sympathetic nerves, as also of the carotid artery, have been removed from the triangular space bounded by the sterno- and thyro-hyoids mesially, by the sterno-mastoid externally, and by the muscular part of the stylo-hyoid superiorly, and in the space thus bounded we see the upper part of the cleido-mastoid muscle, m, externally, and a part of the rectus capitis anticus major internally passing up to take origin in company with each other from the basi-occipital.
t. Body of hyoid bone; the longer cornu, or thyro-hyal, passes backwards in connection with the tendon of the stylo-hyoid, the anterior cornu and arch are concealed from view.
u. Digastric muscle, here represented by a single muscular belly, placed anteriorly and inserted into the symphysis of the lower jaw, and by a tendon taking origin from the paroccipital process and representing the posterior muscular belly of anthropotomy and the single muscular belly of the Carnivora.
v. Mylo-hyoid muscle.
w. Depressores labii inferioris.
x. Insertion of platysma myoides into lower jaw on left side below buccinator, anteriorly to masseter muscle.
x'. Fibres passing off from this cutaneous muscle to end in the moveable tissues round the mouth.
x'. Insertion of platysma myoides into lower jaw of right side cut short.
x"'. Insertion of platysma myoides into manubrium sterni.
x"". Delamination of platysma myoides into two layers.
y. Buccinator muscle.
y'. Masseter muscle, with much less obliquity in its fibres than is usual in Rodents, as necessitated by the relations of the mandible and malar arch. It consists here of two strata as in the Horse, but has of course no antorbital factor as have so many Myomorphous and Hystricomorphous Rodents. It is bounded anteriorly by a stout tendinous band, which prevents the lower jaw to which it is affixed below from being separated beyond a certain distance from the jugal arch, to the freely projecting anterior angle of which it is affixed above. The mobile bifid lip compensates somewhat for this restriction on the opening of the jaws.
z. Internal pterygoid muscle.