_1_, Scapula; _1′_, cartilage of scapula; _4_, lamellar part of
ligamentum nuchæ; _x_, wing of atlas. (After Ellenberger-Baum, Anat.
für Künstler.)
]
The =supraspinous ligament= extends medially from the occipital bone to
the sacrum. From the withers backward it consists of a strong cord of
fibrous tissue, attached to the summits of the vertebral spines. In the
neck and withers it is remarkably modified to form the ligamentum nuchæ,
which requires more extended notice.
The =ligamentum nuchæ= is a powerful elastic apparatus, the principal
function of which is to assist the extensor muscles of the head and
neck. It extends from the occipital bone to the withers, where it is
directly continuous with the supraspinous ligament. It consists of two
parts—funicular and lamellar. The =funicular part= (Pars occipitalis)
arises from the external occipital protuberance and the fossa below it,
and is inserted into the summits of the vertebral spines at the withers.
Two =bursæ= are usually found under it in the adult. The =supra-atloid
bursa= lies between the ligament and the dorsal arch of the atlas. The
=supraspinous bursa= occurs usually over the fourth thoracic spine, but
may be over the third and may extend to the fifth.[31] In the neck the
funicular part consists for the greater part of two bands closely
applied and attached to each other. Near and at the withers it broadens
greatly, forming an expansion three to five inches (ca. 8 to 12.5 cm.)
in width, the lateral margins of which are thin and overlie the
trapezius and rhomboideus muscles. Behind the higher spines it becomes
narrower and thinner, and is continued by the white fibrous lumbo-dorsal
ligament.[32] A mass of fat and elastic tissue lies upon the ligament as
far back as the withers. It varies greatly in amount in different
subjects, and is most developed in stallions of draft breeds, in which
it forms the basis of the “crest.” The =lamellar portion= (Pars
cervicalis) consists of two laminæ separated medially by a layer of
loose connective tissue. Each lamina is formed of digitations which
arise from the second and third thoracic spines and from the funicular
portion, are directed downward and forward, and end on the spines of the
cervical vertebræ, except the first and last. The digitation which is
attached to the spine of the axis is very thick and strong. Behind this
they diminish in size and strength; that to the sixth cervical is quite
thin and feeble, or may be absent.
The =interspinous ligaments= (Ligamenta interspinalia) extend between
the spines of contiguous vertebræ. In the cervical region they are
narrow elastic bands, and in the thoracic and lumbar regions they
consist of white fibers directed obliquely downward and forward.
The =intertransverse ligaments= (Ligamenta intertransversaria) are
membranes which connect adjacent transverse processes in the lumbar
region.