Henry Gray (18251861). Anatomy of the Human Body. 1918.
The Lumbar Nerves (Nn. Lumbales)The medial branches of the posterior divisions of the lumbar nerves run close to the articular processes of the vertebræ and end in the Multifidus.
The lateral branches supply the Sacrospinalis. The upper three give off cutaneous nerves which pierce the aponeurosis of the Latissimus dorsi at the lateral border of the Sacrospinalis and descend across the posterior part of the iliac crest to the skin of the buttock (Fig. 801), some of their twigs running as far as the level of the greater trochanter.
The Sacral Nerves (Nn. Sacrales)The posterior divisions of the sacral nerves (rami posteriores)(Fig. 803) are small, and diminish in size from above downward; they emerge, except the last, through the posterior sacral foramina. The upper three are covered at their points of exit by the Multifidus, and divide into medial and lateral branches.
The medial branches are small, and end in the Multifidus.
The lateral branches join with one another and with the lateral branches of the posterior divisions of the last lumbar and fourth sacral to form loops on the dorsal surface of the sacrum. From these loops branches run to the dorsal surface of the sacrotuberous ligament and form a second series of loops under the Glutæus maximus. From this second series cutaneous branches, two or three in number, pierce the Glutæus maximus along a line drawn from the posterior superior iliac spine to the tip of the coccyx; they supply the skin over the posterior part of the buttock.
The posterior divisions of the lower two sacral nerves are small and lie below the Multifidus. They do not divide into medial and lateral branches, but unite with each other and with the posterior division of the coccygeal nerve to form loops on the back of the sacrum; filaments from these loops supply the skin over the coccyx.