AN ANATOMICAL ANALYSIS OF THE RELATIONSHIPS BETWEEN THE INTERCOSTAL NERVES AND THE THORACIC AND ABDOMINAL MUSCLES IN MAN .1. RAMIFICATION OF THE INTERCOSTAL NERVES

Minute dissection was performed on the ventral primary rami of the fir st thoracic to first lumbar nerves in two halves of an adult male cada ver in order to determine points of origins of muscular branches from the intercostal nerves, Generally, the muscular branches originated in dependently, but the branches supplying the intercostalis intimus and internus tended to originate as a common trunk. The muscular branching patterns were compiled in an illustration, and based on these pattern s the serial homology of the thoracic and abdominal muscles was propos ed. Although the obliquus externus abdominis has been thought to corre spond to the intercostales externi, from these innervation findings it appears to correspond to the intercostales interni. Further, the quad ratus lumborum seems homologous to the intercostales externi.