Henry Gray (18251861). Anatomy of the Human Body. 1918.
The Coccygeal Nerve (N. Coccygeus)The posterior division of the coccygeal nerve (ramus posterior) does not divide into a medial and a lateral branch, but receives, as already stated, a communicating branch from the last sacral; it is distributed to the skin over the back of the coccyx.
6b. The Anterior Divisions
The anterior divisions of the spinal nerves supply the antero-lateral parts of the trunk, and the limbs; they are for the most part larger than the posterior divisions. In the thoracic region they run independently of one another, but in the cervical, lumbar, and sacral regions they unite near their origins to form plexuses.
The Cervical Nerves (Nn. Cervicales)
The anterior divisions of the cervical nerves (rami anteriores), with the exception of the first, pass outward between the Intertransversarii anterior and posterior, lying on the grooved upper surfaces of the transverse processes of the vertebræ. The anterior division of the first or suboccipital nerve issues from the vertebral canal above the posterior arch of the atlas and runs forward around the lateral aspect of its superior articular process, medial to the vertebral artery. In most cases it descends medial to and in front of the Rectus capitis lateralis, but occasionally it pierces the muscle.
The anterior divisions of the upper four cervical nerves unite to form the cervical plexus, and each receives a gray ramus communicans from the superior cervical ganglion of the sympathetic trunk. Those of the lower four cervical, together with the greater part of the first thoracic, form the brachial plexus. They each receive a gray ramus communicans, those for the fifth and sixth being derived from the middle, and those for the seventh and eighth from the lowest, cervical ganglion of the sympathetic trunk.
The cervical plexus is formed by the anterior divisions of the upper four cervical nerves; each nerve, except the first, divides into an upper and a lower branch, and the branches unite to form three loops. The plexus is situated oppostie the upper four cervical vertebræ, in front of the Levator scapulæ and Scalenus medius, and covered by the Sternocleidomastoideus.
Its branches are divided into two groups, superficial and deep, and are here given in tabular form; the figures following the names indicate the nerves from which the different branches take origin: