The probable source and circulatory pathways of the human cerebrospinal fluid have been ascertained in comparatively recent years, although Magendie1 published his observations on the character of the fluid just a century ago. The origin of the fluid has yet to be proved absolutely, although the choroid plexus theory seems almost incontrovertible.
During the past ten years, Weed,2 by splendid experimental work, has cleared up many perplexing points in what might be called the life history of this body fluid, and necessarily I shall quote him extensively. Clinical application of his studies has shown that facts demonstrated in experimental animals are entirely analogous to conditions found in the human being. In no part of the body is physiologic control of anatomic knowledge more necessary than in a study of the cerebrospinal fluid and its pathways. Only those findings can be accepted as final which are supported by experimental