LUMBAR PUNCTURE l8l 



tion is that the case is one of tuberculous meningitis. In acute 

 meningitis due to other bacteria the chief cell is the poly- 

 nuclear leucocyte; this may be recognized by its larger size, 

 its twisted (apparently multiple) nucleus, and, if the staining 

 method has been appropriate, by the presence in its proto- 

 plasm of minute granules which stain with eosin. The fluid 

 may also contain red blood-corpuscles and shreds of fibrin. 



(c) Chemical Cerebro-spinal fluid removed from a person 

 who is not suffering from meningitis contains a very minute 

 amount of albumen, while when the meninges are inflamed 

 the quantity is greatly increased. The method of testing these 

 small amounts of albumen quantitatively is hardly within the 

 reach of practitioners; if a considerable amount of fluid has 

 been obtained, a small quantity should be tested by heat and 

 acetic acid, and the amount of opacity noted. This should be 

 very slight, not more than what would be called a " faint haze " 

 in urinary work. 



Another test is that for the presence of sugar.* For this 

 (as for the testing for albumen) the clear supernatant fluid left 

 after oentrifugalization should be used. In health, sugar is 

 present in considerable amount (about 0*1 per cent), and 

 Fehling's solution is vigorously reduced; in meningitis, sugar 

 is either reduced to a trace or, much more frequently, com- 

 pletely absent. It is not a certain test, but next to the pre- 

 sence of cells and bacteria it is, perhaps, the most certain 

 indication of meningitis. 



There are also characteristic chemical changes in uraemia. 

 In health the cerebro-spinal fluid contains about 0*02 to 0*04 

 per cent, of urea, 0^7 per cent, of chlorides, and has a freezing- 

 point of -0-56 C., or thereabouts. In renal disease in which 

 the kidneys are acting well these figures are but slightly dis- 

 turbed, but in uraemia there is abundant evidence of retention 

 of soluble substances. The urea increases greatly the maxi- 

 mum I have seen being o - 4 per cent. the chlorides may rise 

 to i per cent., and the freezing-point is depressed. I believe 

 this to be the simplest test of the functional capacity of the 

 kidney, the chemical examinations being easy in a substance 



* It is sugar (glucose), as may be demonstrated by the phenylhydrazin and 

 fermentation tests. For the latter, however, the fluid must be concentrated, 

 as the small amount of CO., given off from an unconcentrated specimen is 

 soluble in the fluid. 



