264 CLINICAL BACTERIOLOGY AND H^EMATOLOGY 



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 haemor- 

 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 eifused. 



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 

 (similar cells to those shown on Plate X., Fig. 3) may appear in 

 the fluid after a cerebral haemorrhage. They do not make their 

 appearance until three or four days after the blood has been 

 poured out. 



Hemorrhage into the meningeal cavities or into the ventricles is, of 

 course, accompanied by blood in the cerebro-spinal fluid. This 

 may be found in cases of fracture of the skull, especially of the 

 base, or of the spinal column, or in contusion of the brain, and it 

 is worth noting that in some cases there has been great relief of 

 the symptoms after the fluid has been drawn off'. Lumbar puncture 

 should always be remembered as a means of diagnosis in patients 

 found unconscious. 



"Septic" Meningitis — i.e., that due to the meningococcus, 

 pneumococcus, streptococcus, typhoid bacillus, etc. — is character- 

 ized by the presence of large numbers of polynuclear cells in the 

 fluid (see p. 152). In all cases the numbers tend to be more 

 numerous than in tuberculous meningitis, and may run into 

 hundreds of thousands per cubic millimetre, in which case the 

 fluid resembles watery pus. 



The importance of this fact is very great, and the discovery of 

 polynuclear leucocytosis has led to the discovery that mild cases 



