. Diseases of the nervous system . rosis, but they usuallydevelop in youth; hence early disturbances in the formation of the spinalcord, and injuries occurring prior to this, must also be considered. The conclusion is obvious that in many cases in which the first signsof syringomyelia appear during the course of infectious disease, for example,enteric fever, the microorganisms or toxins which are generated in such affec-tions accumulate in abnormal diverticula of the central canal, and thence setup pathologic processes. Whether this be true or not, the condition and localization of the syringo
. Diseases of the nervous system . rosis, but they usuallydevelop in youth; hence early disturbances in the formation of the spinalcord, and injuries occurring prior to this, must also be considered. The conclusion is obvious that in many cases in which the first signsof syringomyelia appear during the course of infectious disease, for example,enteric fever, the microorganisms or toxins which are generated in such affec-tions accumulate in abnormal diverticula of the central canal, and thence setup pathologic processes. Whether this be true or not, the condition and localization of the syringo-myelitic changes which have been described may be deduced from other wellknown physiologic facts and many of the symptoms which necessarily arisein this affection. Before attempting this, I must state that, besides affecting the gray sub-stance and the posterior columns, the proliferative and destructive processesgoing on around the spaces and cavities may also implicate the lateral columns, SYRINGOMYELIA 591 Accumulation of glia. Pyramids Olives Fig. ISO.—Transverse Section through the MedullaOblongata in a Case of Syringobulbia. (After ) for they are either exposed to a marked lateral pressure from the proliferatedglia masses or are directly implicated in the chronic degeneration. Frequently the entire spinal cord is permeated by cavities and spaces;sometimes, however, the cervical and dorsal portions alone may be implicated,while syringomyelia limitedsolely to the lumbar por-tion is very rare. Usuallythe segments of the cer-vical enlargement, particu-larly the lower ones, aremost markedly affected. It is significant thatnot rarely the medulla ob-longata also is implicatedin this peculiar cavity for-mation, that, therefore, asyringobulbia anomaly is usuallyunilateral at the height ofthe fourth ventricle in theregion of the nucleus of thepneumogastric, and thencepasses anteriorly and lat-erally. In other cases thedestruction is bilateral but asymmet
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