The Muscles of the Back can again be divided into transverse and longitudinal. The transverse muscles are those which connect the shoulder girdle with the spinal column, and the longitudinal ones those that cause extension of the back and the movements of the pelvis (as in locomotion), which correspond with those of the spinal column. The movements of the head on the spinal column will be considered in another section.

Fig. 35. - Muscles of the Back.

The muscles are arranged in four layers. Starting with the most superficial they are:

1. Trapezius and latissimus dorsi.

2. Levator anguli scapulae and rhomboids.

3. Serrati postici superior and inferior, splenius capitis and splenius cervicis.

4. Erector spinae and complexus.

Beneath these muscles are a large number of smaller ones that move the vertebrae on one another - e.g., rotatores, interspinals, etc.