430 THE EXPERIMENTAL PRODUCTION OF AN INTERNAL HYDROCEPHALUS. 



ventricular injection of India ink demonstrated that the obstruction to flow of the 

 cerebro-spinal fluid occurred, in the different animals, either at the foramen of 

 Munro, in the aqueduct of Sylvius, or most frequently, at the foramen of Magendie. 

 It must be emphasized that in many cases the ventricular dilatation was markedly 

 asymmetrical (the greater enlargement being on the side of the injection) and that 

 the ventricular wall was often irregularly eroded. The intraventricular accumu- 

 lation of fluid was associated with a sterile inflammatory process. 



An attempt to produce an internal hydrocephalus in kittens was made by Burr 

 and McCarthy (1900). These authors described a case of internal hydrocephalus 

 in man with a macroscopically boggy ependyma. Microscopically, the sections 

 showed proliferation of ependyma and neuroglia, interstitial infiltration of the 

 choroid plexuses, and some perivascular invasion with inflammatory cells. As the 

 nature of the lesion in this case suggested to these workers a toxic irritant, intra- 

 ventricular injections of sterilized urine, glycerine extract of the adrenals, tuber- 

 culin, hydrochloric and carbolic acid were made in kittens. No dilatation of the 

 cerebral ventricles occurred in these animals, though similar ependymal and glial 

 changes were reproduced. 



Flexner (1907) recorded the occasional production of an internal hydrocephalus 

 in monkeys following lumbar subarachnoid injection of meningococci. Of one 

 subacute case of meningitis he wrote: 



"A striking feature of the sections is derived from the width of the ventricles. As a 

 rule, these appear as slits in the sections; in this case they are wide cavities. Usually, the 

 ependymal epithelium is regular and relatively high; in this case, it is often depressed or 

 flattened, and a considerable flattening of the choroid plexus, toward the wall of the ven- 

 tricle, is noticeable. A considerable degree of sub-epithelial cellular proliferation has taken 

 place in the walls of the lateral and fourth ventricles. Leucocytes are moderately abundant 

 in the ventricles." 



METHOD OF INVESTIGATION. 



The method of investigation in this study developed out of the idea that it 

 would be possible to produce an internal hydrocephalus in animals if a sterile 

 meningitis of appropriate type and distribution could be caused. This assumed 

 that the meningeal variety of obstruction to flow of the cerebro-spinal fluid was an 

 experimental possibility and the agencies were selected with this end in view. 



In a previous report (Weed, 1917) notation was made of the fact that, following 

 the subarachnoid injection of inert carbon particles, evidence of phagocytosis on 

 the part of the cells lining the subarachnoid space could be made out. By increasing 

 the quantity of this inert substance it was hoped that a more extensive reaction of 

 inflammatory cells and of the arachnoidea could be brought about. Quite similarly 

 it was proposed to make subarachnoid or intraventricular injections of other insol- 

 uble particles. It was desired primarily to reproduce a hydrocephalus in a very 

 young animal, so that a typical enlargement of the head, comparable to the fairly 

 common condition in children, might be produced. To accomplish this, it was felt 

 that the experimental procedure must be necessarily simple and uninvolved. 



Fortunately almost the first technical procedure resulted in the production of a 

 typical internal hydrocephalus. A litter of kittens two weeks old was obtained; 



