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In our deafborn cat the hydrops ventriculi is nevertheless secondary 



to a morbid process situated elsewhere. 



For in the left hemisphere are found the residua of a process of 

 encephalitis having occurred long ago, in casu before birth. 



This focus is situated in the left corona radiata and in the radiation 

 of the corpus callosum. The cortex remains uninjured. Loss of fibres, 

 tumefaction of glia-elements, formation of cavities and neo-formation 

 of vessels mark the place where the focus is found. 



Frontalward its boundary nearly coincides with the place where 

 the gyrus lateralis divides into a gyrus ecto- and ento-lateralis. 

 Thence it expands below the gyri supra- and ecto-sylvii mediales, 

 caudalward not passing beyond the fissura ectosylvia posterior. 

 There is a secondary atrophy of the medullated radiations of the 

 following convolutions : the gyrus splenialis, supra-splenialis, eCoO- 

 lateralis, supra-sylvius medialis and ecto-sylvius medialis and in the 

 lateral portion of the gyrus ecto-sylvius posterior. (Speaker demon- 

 strates the position of this focus with the aid of drawings, prepa- 

 rations and micro-photograms). 



This morbid process has entailed consequences. 



1. The hydrocephalus interims mentioned before, which has distended 

 the lateral ventricles, the third ventricle, the aquaeductus and the 

 fourth ventricle, in the latter mere especially the reeessus lateralis. 



2. The macroscopically visible atrophy of the radiations towards 

 the aforesaid convolutions and in the fibres of the corpus callosum. 



3. The atrophy of ceils, more intensive in the before-mentioned 

 convolutions, though also very evident in other convolutions of the 

 left hemisphere and likewise in the right hemisphere. 



A loss of cells does not exist in the anterior convolutions, it begins 

 far behind the zone where the pyramides of Betz are found. The 

 posterior pole was too much damaged to allow of any examination. 

 But in the medial portions of the brain the degeneration is the 

 following : 



The loss and atrophy of cells is localized in the medial layers of 

 cells of the cortex. The first layer of granular cells and that of the 

 small pyramides are only slightly damaged, but the 4 th stratum or 

 interior granular layer and the 5 th so-called sub-granular layer of 

 the pyramides have lost all or a great number of the cells, the 6 th 

 or polymorphous layer of cells being again intact. 



4. A macroscopically visible atrophy] of thejventral nucleus of 

 the left thalamus opticus, which has almost entirely disappeared at 

 its frontal end and has lost cells as well as fibres. 



5. A very slight atrophy in the most caudal part of the left 



