172 CEREBRAL LOCALIZATION 



is a long history of headache, vomiting, or other signs, 

 previous to the development of spasticity or cranial 

 nerve palsy. 



In other cases, misleading localizing signs may 

 arise from patches of secondary thrombosis, spreading 

 oedema, or meningitis ; but none of these are common. 



The suspicious feature about all the signs here 

 mentioned is their late development. Localizing 

 symptoms appearing when headache, vomiting, optic 

 neuritis or other evidences have been present for 

 months or years are little to be trusted. Early 

 localizing signs, on the other hand, are trustworthy 

 in the main. 



A few words may be said about the significance 

 of ataxia. This is of course evidence of a lesion of 

 the cerebellum, but it may be seen in other conditions 

 also. Putting aside ataxia due to affections of the 

 labyrinth, Friedreich's ataxia, and other general 

 nervous diseases, it may also be caused by a tumour 

 in the neighbourhood of the red nucleus in the 

 isthmus, or in the pons. 



THE CEREBROSPINAL FLUID. 



This fluid is clear, watery, and of low specific 

 gravity ; it contains almost no albumin, but some 

 sugar. Until recently this reducing substance was 

 thought to be a pyrocatechin body. It contains no 

 cells in health, nor does it contain the antitoxins, 

 opsonins, or alexins which are present in plasma, 

 lymph, and most serous fluids. This explains the 

 great liability to septic meningitis after injuries to 

 or operations on the central nervous system. As 



