Observations on the pia-arachnoid of the anterior median fissure and the posterior median sulcus of the fetal spinal cord of the albino mouse.

In the spinal cord of mouse fetuses, the pia-arachnoid lying in relation to the dorsal extremity of the posterior median septum forms two prolongations delimited laterally by veins that drain into the posterior spinal vein. A similar arrangement was met with in the anterior spinal veins. Definite cell columns in some instances and cell clusters in others were recognized in the arachnoid prolongations. The possibility that these arachnoid prolongations with the cells they contain constitute a route connecting the spinal cerebro-spinal fluid with the venous blood stream is discussed.