THE EXPERIMENTAL PRODUCTION OF AN INTERNAL 



HYPROCEPHALUS. 



BY LEWIS H. WEED. 



INTRODUCTION. 



The pathological condition of internal hydrocephalus is intimately connected 

 with abnormalities of the production or absorption of cerebro-spinal fluid. The 

 first explanation of this condition an increased elaboration of the fluid by the 

 choroid plexuses remains a hypothetical possibility. Obstruction to the normal 

 pathways of drainage of the fluid has been many times demonstrated anatomically, 

 so that now this idea of the origin of the disease may be considered to rest on a 

 firm basis. It is with the experimental production of that type of hydrocephalus, 

 due to obstruction to the flow of the cerebro-spinal fluid through its normal channels, 

 that this paper will deal. 



To insure a more complete understanding of the anatomical problems under- 

 lying internal hydrocephalus, a short review of the essential morphological and 

 physiological features of the pathways of the cerebro-spinal fluid will be given. 

 The conception that the greater part of the cerebro-spinal fluid is produced by the 

 choroid plexuses of the cerebral ventricles is no longer strongly controverted ; when 

 first advanced, it had only the glandular histology of the plexus to support it (Faivre, 

 1853; Luschka, 1855), but much later a combination of pharmacological, histologi- 

 cal, and pathological observations indicated beyond question the essential role of 

 these plexuses in the elaboration of this body-fluid. From a summary of this evi- 

 dence and from personal study Mott (1910) suggested the term "choroid gland" 

 for these vascular structures. More recently embryological studies related the 

 first extraventricular flow of the fluid to the initial tufting of the plexuses (Weed, 

 1916 a and b; 1917). Pathologically, the production of an internal hydrocephalus 

 by tumors occluding the ventricular passages has been recognized for years as 

 affording evidence of an intraventricular source of the fluid. 



From the choroid plexuses the fluid is poured into the cerebral ventricles which 

 are lined by ependymal cells of ectodermal origin. The fluid from the lateral 

 ventricles escapes through the foramina of Munro into the third ventricle, thence 

 through the aqueduct of Sylvius into the fourth. Additions to the fluid are made 

 by the choroid plexuses of the third and fourth ventricles. From the fourth 

 ventricle this fluid passes into the mesodermal subarachnoid spaces through the 

 foramina of Magendie and of Luschka, if these be actual openings, or at least 

 through permeable membranes if the patency of the foramina be questioned. 



The cerebro-spinal fluid leaving the ventricular system, is distributed from the 

 cisterna cerebello-medullaris, which it first reaches on leaving the fourth ventricle. 

 In the comparatively large channels about the base of the brain the flow is rapid 

 and great; down the cord the dispersion is also fairly efficient, but over the con- 



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