. A text-book of medicine for students and practitioners . SYSTEM and that its walls arc covered by cylimlrical epitlieliuiu. Sligiit degrees ofhvdroinyelus, in wiiich the dilated central canal has a diameter of 1 nun. or]..) mm., are not infrequently found. The dilatation usually extends over(iiilv one segment of the cord. Greater degrees of hydromyelus, where thecentral canal is dilated to a diameter of cm. or 1 cm. and the longitudinalextent is greater, are much rarer. In regard to the origin of hydromyelus, we may assume, according to theteaching of Leyden, that the cause is quite gene
. A text-book of medicine for students and practitioners . SYSTEM and that its walls arc covered by cylimlrical epitlieliuiu. Sligiit degrees ofhvdroinyelus, in wiiich the dilated central canal has a diameter of 1 nun. or]..) mm., are not infrequently found. The dilatation usually extends over(iiilv one segment of the cord. Greater degrees of hydromyelus, where thecentral canal is dilated to a diameter of cm. or 1 cm. and the longitudinalextent is greater, are much rarer. In regard to the origin of hydromyelus, we may assume, according to theteaching of Leyden, that the cause is quite generally some anomaly of de-velopment in the formation of the central canal. The hypothesis of Lang-hans that processes of stasis in the central canal, such as compression of theupper end hy a tumor in the posterior cranial fossa, may lead to hydromyelus,is certainly not a])])licahle to the great majority of cases. The conditions are different in syringomyelia, which is of much gicatcrpractical importance. In this affection, according to many investigators. Fig. 192.—Syringomyelia of the cervical cord. Central gliosis and cavity formation. (From F. Schultze.) (Westphal, Simon, F. Schultze, J. Hoffmann, and others), the whole processapparently begins with a gliomatous new formation or transformation oftissue in the central portions of the spinal cord. This peculiar process, whichprobably starts in the ependymal cells about the central canal, is called cen-tral gliosis. It consists of a replacement of nerve tissue by fibrous glia central gliosis, which extends toward either the posterior or the anteriorhorns, has a decided tendency to break down and thus to form secondarycavities, which unite with the central canal or remain independent, and thesecavities may extend longitudinally in the central portions of the cord withnumerous ramifications and projections. To this secondary formation ofcavities we give the name of syringomyelia (vide Yig. 192). In this con-dition the
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