Henry Gray (18251861). Anatomy of the Human Body. 1918.
Muscles.The muscles proper of the back are so obscured by those of the upper extremity (Fig. 1211) that they have very little influence on surface form. The Splenii by their divergence serve to broaden out the upper part of the back of the neck and produce a fulness in this situation. In the loin the Sacrospinales, bound down by the lumbodorsal fascia, form rounded vertical eminences which determine the depth of the spinal furrow and taper below to a point on the dorsal surface the sacrum. The continuations of the Sacrospinales in the lower thoracic region form flattened planes which are gradually lost on passing upward.