444 THE EXPERIMENTAL PRODUCTION OF AN INTERNAL HYDROCEPHALUS. 



cortex) of practically all of the essential intraventricular markings and structures; 

 these are altered somewhat by the dilatation of the ventricles but remain easily 

 identified. It must be granted, then, that the thinning of cerebral cortex in such 

 internal hydrocephalus is the result largely of a rearrangement of tissues a stretch- 

 ing and compression of the existing brain-tissue to cover the enlarging ventricles. 

 In this enlargement some destruction of tissue may take place, but the essential 

 process is a rearrangement of the bulk of cerebral tissue. 



The obstruction to flow of the cerebro-spinal fluid, brought about by intra- 

 ventricular or subarachnoid injection of lampblack, must be assumed, then, to be 

 due to aggregation of these granules into an impervious mass, the essential and 

 ultimate matting together being accomplished probably by an inflammatory pro- 

 cess. Because of this obstruction, enlargement of the lateral ventricles follows, 

 necessitating a diminution in thickness of the cortex cerebri, brought about by some 

 tissue compression (as in adults) and by compression and readjustment of brain 

 bulk (as in kittens). 



SUMMARY. 



An acute internal hydrocephalus may be produced by the intraventricular or 

 subarachnoid injection of suitable amounts of a suspension of lampblack. In 

 kittens the degree of this internal hydrocephalus is extreme, being associated with a 

 marked enlargement of the head and other changes in the general appearance. 

 This extreme dilatation of the ventricles with thinning of the cerebral cortex in 

 kittens has been brought about in 10 days. In adult animals a similar dilatation 

 of the lateral ventricles, but of lesser degree, may be caused by the same procedure. 

 The internal hydrocephalus, produced experimentally in this way, is comparable 

 in detail to similar conditions in man. 



