438 THE EXPERIMENTAL PRODUCTION OF AN INTERNAL HYDROCEPHALUS. 



to this individuality no general rule can be formulated. The generalizations recorded 

 will remain more or less as impressions, but are of importance in the discussion. 



One adult animal subjected to a subarachnoid injection of "carbon flour" 

 (in which the granulation is quite coarse) showed really no clinical signs of acute 

 cerebral pressure, but on being sacrificed after several months exhibited some 

 enlargement of the lateral ventricles. Another cat was given a subarachnoid 

 injection of lycopodium spores (sterilized by boiling). The cat remained normal 

 and active for 6 months; it was then sacrificed for pathological control. No abnor- 

 mality existed except a widespread distribution of the lycopodium throughout the 

 subarachnoid space (fig. 4). To further control the injection of granules in the 

 subarachnoid space, several animals were given injections of cinnabar, similar in 

 amount to those of lampblack. None of these animals showed any signs of increased 

 intracranial pressure and, post mortem, no ventricular dilatation was present (fig. 2). 

 Another animal was given repeated massive doses of the cinnabar into the sub- 

 arachnoid space; the result of these repeated huge doses was a gradual abolition 

 of function of the hind-legs, without signs of an increase in intracranial pressure. 

 The peculiar power of the carbon granules in causing increased pressures within 

 the central nervous system, with resulting hydrocephalus, seems therefore indicated. 



GROSS PATHOLOGY OF THE CONDITION. 



The diagnosis of the lesion of the central nervous system after the intraven- 

 tricular or subarachnoid injection of lampblack, cinnabar and other participate 

 substances, naturally depends largely upon the pathological picture post mortem, 

 though a good conception of the lesion may be had during life (especially in the 

 kitten). In these experiments all of the animals were injected with 10 per cent 

 formalin through the aorta and the tissues allowed to harden for some time before 

 the initial dissection and final immersion in formalin. The bony skull was then 

 removed in the adults and the brain preserved with the dura intact. In kittens, 

 however, due to the widely dilated sutures, etc., the brain was not removed, but 

 was studied in situ in the skull by means of gross sections. 



In both kittens and adult cats, in which intraventricular or subarachnoid 

 injections of lampblack were made, the essential pathology of the central nervous 

 system concerns a marked dilatation of the lateral cerebral ventricles with altera- 

 tions of the cortex, a typical internal hydrocephalus. As the condition is quite 

 different in the younger animals, as compared with the adults, the descriptions of 

 the lesions will be given separately. Control animals, receiving similar injections 

 of other granules, showed no abnormality of the central nervous system. 



KITTENS. 



The gross pathological lesion in the kittens surviving the intradural injection 

 of lampblack for 10 days or over is practically identical in the different specimens. 

 Reduced to simplest form, the abnormality consists in a tremendous and remark- 

 able dilatation of the cerebral lateral ventricles (figs. 10, 14, 16). This increase in 

 size of the lateral ventricles, associated with an enlargement of the kitten's head, 

 results in a marked thinning of the cerebral cortex (figs. 10, 14, 16, and 20). In 



