The lower intercostal nerves supply the Intercostales and abdominal muscles; the last three send branches to the Serratus posterior inferior.
2.
It is situated at the junction of the thoracic and lumbar regions : it is of an irregularly quadrilateral form, broader than the serratus posterior superior muscle, and separated from it by a wide interval.
3.
They run through or beneath the Longissimus dorsi to the interval between it and the Iliocostales, and supply these muscles; the lower five or six also give off cutaneous branches which pierce the Serratus posterior inferior and Latissimus dorsi in a line with the angles of the ribs.