「The Spinalis dorsi, the medial continuation of the Sacrospinalis, is scarcely separable as a distinct muscle.
It is situated at the medial side of the Longissimus dorsi, and is intimately blended with it; it arises by three or four tendons from the spinous processes of the first two lumbar and the last two thoracic vertebrae: these, uniting, form a small muscle which is inserted by separate tendons into the spinous processes of the upper thoracic vertebræ, the number varying from four to eight.
It is intimately united with the Semispinalis dorsi, situated beneath it.」