ENTOZOA IN THE NERVOUS SYSTEM. 195 



of the vesicular worijos by the performance of the 

 operation of trephining. 



The progressive and gradual compression exerted 

 by the hydatid tumours does not at first produce 

 any other effects than those which have been already 

 mentioned ; but, after a time, nev7 lesions present 

 themselves. These may be of a local character, and 

 occur cliiefly around the tumour, such as congestion, 

 inflammation, softening, or induration ; or they may 

 be more general, such as sub-arachnoidean effusion, 

 serous infiltration into the cavities of the ventricles 

 or into the cavity of the arachnoid membrane, and 

 cerebral hsemorrhage. 



o 



Upon a consideration of the symptoms, and of 

 the appearances found on making post-mortem exa- 

 minations, it is e\T.dent that the hydatid tumour 

 must sometimes have reached a very large bulk 

 before the production of any marked functional 

 derangement. In this respect, as in that of the 

 anatomical lesions which they occasion, the hydatids 

 of the nervous centres do not differ from any other 

 species of intra-cranial tumour, which has a slow 

 development, and ultimately attains to a large size. 



The principal and most frequent symptoms of 

 hydatid tumours situated in the brain are headache, 

 convulsive paroxysms, vomiting, syncope, and dis- 

 turbance of the motor and sensory functions, and of 

 the intellectual faculties. 



Headache is a very common, and often the first, 

 symptom ; it is sometimes continuous, but more 

 generally it occurs in paroxysms ; it is very severe 

 occasionally, and usually becomes more marked as 

 the affection advances. Neuralgic pains, simulating 



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