CYTO-DIAGNOSIS 263 



the diagnosis is either insular sclerosis or hysteria, the presence 

 of a moderate leucocytosis tells strongly in favour of the former. 

 Similarly in the diflFerential diagnosis between tabes and peripheral 

 neuritis, and between general paralysis and most of the diseases 

 which it simulates. It is to be noted that excess of lymphocytes 

 in the cerebro-spinal fluid is a very early and a very constant finding 

 in these affections, and often occurs long before the diagnosis can 

 be made by ordinary clinical methods. Its absence is most im- 

 portant as a negative test ; its presence is only equally important 

 if the diagnosis certainly lies between a disease in which this sign 

 is present and one in which it is absent. 



Syphilis. — In syphilis without involvement of the meninges 

 the cerebro-spinal fluid remains normal, but with the slightest 

 involvement of these structures a lymphocytosis occurs. The 

 Wassermann reaction is present, and this is of the utmost import- 

 ance as enabling us to distinguish between a syphilitic lymphocy- 

 tosis and one due to other causes. Where its presence or absence 

 cannot be investigated, Noguchi's method may be used. To 

 I part of cerebro-spinal fluid add 5 parts of a 10 per cent, solution 

 of butyric acid, and boil the mixture for a few seconds. Then add 

 I part of normal caustic soda solution, and again boil. An im- 

 mediate and marked turbidity of the fluid, which deposits flocculent 

 masses and becomes clear, indicates syphilis. Some turbidity 

 occurs with normal fluids, and a few tests should be done on 

 syphilitic and non-syphilitic fluids before the test is used in 

 diagnosis ; but after a very moderate amount of experience the 

 test is one of great value. All three tests — the enumeration of the 

 cells, the Wassermann reaction, and the Noguchi reaction — should 

 be used in all cases. 



Tuberculous Meningitis has been described already. The 

 lymphocytes may be so numerous as to make the fluid very 

 slightly turbid as compared with pure water, or may number 

 10,000 per cubic millimetre. There is a slight excess of 

 albumen, often no sugar, and sometimes albumose is present. 

 Occasionally the films show a few polynuclear cells, but they are 

 seldom numerous. 



H/EMORRHAGE. — With a deep cerebral haemorrhage the fluid is 

 usually clear for two or three days, and then tinged with blood and 

 blood pigment ; the time necessary for this to occur depends on 

 the depth of the haemorrhage from the surface or from the cerebral 

 ventricles. 



