Note 40 — PART I.—MORPHOLOGY AND PHYSIOLOGY (continued 5)

This has been shown to be the case by Michels, who states that each commissure is formed of three parallel bundles of elementary nerve-fibres, which pass continuously from one end of the ventral or nervous cord to the other. “The commissures take their origin neither out of a central punctsubstanz (or marksubstanz), nor from the peripheral ganglion-cells of the several ganglia, but are mere continuations of the longitudinal fibres which decrease posteriorly in thickness, and extend anteriorly through the commissures, forming the œsophageal ring, to the brain.”