280 THE SPINAL NERVES. 



to d 12, external muscular branches of the posterior primary divisions of the twelve dorsal nerves on the 

 right side ; d 1', to d 6', the internal cutaneous branches of the six upper dorsal nerves on the left side ; 

 d 7' to d-12', cutaneous branches of the six lower dorsal nerves from the external branches; I, I, 

 external branches of the posterior primary divisions of several lumbar nerves on the right side piercing 

 the muscles, the lower descending over the gluteal region ; I', I', the same more superficially on the left 

 side (the cutaneous branches of the lower dorsal and upper lumbar nerves are represented as piercing 

 the latissimus too high) : s, s, on the right side, the issue and union by loops of the posterior primary 

 divisions of four sacral nerves ; s', s', on the left side, cutaneous filaments from the internal branches 

 of the lower lumbar and upper sacral nerves. 



CERVICAL NERVES (excepting the siiboccipital}. The external branches give 

 only muscular offsets?, and are distributed to the splenius and the slender muscles 

 prolonged to the neck from the erector spinse, viz., the cervicalis ascendens, and 

 the transversalis cervicis with the trachelo-mastoid. That of the second nerve is 

 the largest of the series of external branches of the cervical nerves, and is often 

 united to the corresponding branch of the third. 



The internal branches, larger than the external, are differently disposed at the 

 upper and the lower parts of the neck. That of the second cervical nerve is named, 

 from its size and destination, the great occipital, and requires separate notice. The 

 rest are directed inwards to the spinous processes of the vertebrae. Those derived 

 from the third, fourth, and fifth nerves pass over the semispinalis and beneath the 

 complexus, giving offsets to those muscles and to the multifidus, and, having 

 reached the spines of the vertebrse, pierce the splenius and trapezius, to be dis- 

 tributed in the integument over the latter muscle. From the cutaneous branch of 

 the third nerve an offset passes upwards to the integument on the lower part of 

 the occiput, lying at the inner side of the great occipital nerve ; this is sometimes 

 called the third occipital nerve. 



Between the inner branches of the first three or four cervical nerves, beneath the corn- 

 plexus, there are frequently communicating loops ; this communication has been designated 

 by Cruveilhier the posterior cervical plexus. 



The internal branches from the lowest three cervical nerves are placed beneath 

 the semispinalis muscle, and end in the muscular structure, without furnishing any 

 offset to the skin. These three nerves are the smallest of the series. 



The great occipital nerve is directed upwards across the inferior oblique muscle, 

 and is transmitted to the surface through the complexus and trapezius muscles, 

 giving twigs to the complexus. Ascending with the occipital artery, it divides into 

 branches which radiate over the back of the head, the most external communicating 

 with the small occipital nerve. 



Varieties. The great occipital nerve occasionally sends a branch to the auricle, or replaces, 

 to a greater or less extent, the small occipital nerve (p. 286). The external division of the 

 second nerve is said to give off a cutaneous branch sometimes, or a twig to the superior 

 oblique. Either the sixth or the eighth cervical nerve may furnish a cutaneous branch. On 

 the other hand, the cutaneous branch of the fifth is sometimes wanting. 



DORSAL NERVES. The external branches increase in size from above down- 

 wards. They are directed through or beneath the longissimus dorsi to the space 

 between that muscle and the ilio-costalis or accessorius, and supply the several 

 divisions of the erector spinae. The lower five or six nerves give cutaneous twigs, 

 which are transmitted to the integument in a line with the angles of the ribs. 



The internal branches of the upper six or seven dorsal nerves pass backwards 

 in the interval between the multifidus spinse and the semispinalis muscle ; they 

 supply the transverso-spinales muscles, and become cutaneous by the side of the 

 spinous processes of the vertebras. The cutaneous branch of the second nerve, and 

 sometimes others, extend outwards over the scapula. The internal branches of the 



