50 PHYSIC 



hydro-cephalism results from non-escape and consequent 

 accumulation, or from over-production, of cerebro-spinal 

 fluid, with consequent cortico-cerebral ballooning and over- 

 development of the cranium to meet the increased skeletal 

 requirements of the condition. 



To a certain extent hydro-myelia may be said to consist 

 of like increase of fluid in the central canal of the cord, and 

 to represent a mechanical distension of its lumen, with 

 mechanical interference with its nutrition and functional 

 powers, which may ultimately assume proportions incom- 

 patible with the maintenance of life ; it is also conceivable 

 that it may precede and initiate the condition known as 

 syringo-myelia, in which case the over-distended central 

 canal limiting structures finally give way, and allow the 

 surrounding neuroglial elements of the cord to be inun- 

 dated with the imprisoned cerebro-spinal fluid, and to be 

 thereby disintegrated and finally washed out of it, reduc- 

 ing it to the condition of a hollow tube, bereft of the 

 nutritive plasma whereby the spinal neurons are enabled 

 to live, and of the physical supports to which they have 

 been accustomed to attach themselves, until they perish 

 from inanition and mechanical disturbance. 



In cases of syringo-myelia not preceded by hydro-myelia, 

 we may infer that the endothelial lining of the central 

 canal suffers a solution of continuity from some intrusive 

 cause and fails to resist the insinuation of the cerebro- 

 spinal fluid, with the attendant vital and mechanical 

 changes, due to admixture of a more or less toxic medium 

 with the neuronal pabulum, and the incidence of nervine 

 changes, due to the destructive progress of the disease 

 created, in accordance with local neuronal implication, 

 until the spinal cord, at and below the seat of attack, 

 becomes more or less completely hollow and functionless, 

 and the structures innervated thereby become degenerated 

 and, in many cases, entirely removed. 



Of course, for such occurrences there must be an array 

 of original and acquired etiological factors of a formidable 

 order, both predisposing and exciting, the determination 

 of the manner of whose working can only be dimly 

 guessed at, but a knowledge of which, if not utilitarian, 

 should be scientifically interesting and very informative, 



