CYTO-DIAGNOSIS 243 



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. 



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, and may number 

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

 albumin, no sugar, and sometimes albumose is present. Occa- 

 sionally the films show a few polynuclear cells, but they are never 

 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. 



When you find blood in the cerebro-spinal fluid, make sure that 

 it does not come from the parietes. If this is the case, it will be 

 most abundant or limited to the commencement of the flow, and 

 if much is present the fluid will coagulate. If it is due to a lesion 

 it will be intimately mixed with the fluid, and will not coagulate. 

 After blood has been present in the cerebro-spinal fluid for about 

 two days, part of the haemoglobin is converted into a yellow 

 pigment ; if, therefore, after centrifugalization the supernatant 

 fluid is yellow, it indicates that the blood was actually present in 

 the cerebro-spinal fluid whilst in the body, and that the hsemor- 

 rhage had occurred two days or more previously. If the super- 

 natant fluid is colourless, the blood came from the puncture, or 

 had only been recently effused. 



If, as sometimes happens, you can only get a few drops of fluid 

 from a lumbar puncture, it is not wise to attach any importance 

 to the presence of a moderate amount of blood. The needle 

 always picks up some corpuscles in its passage through the 

 parietes, and these may be quite obvious if not diluted with a 

 considerable amount of fluid. 



Large endothelial cells containing numerous red corpuscles 



16 — 2 



