LUMBAR PUNCTURE 153 



presence in its protoplasm 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 which has almost escaped notice, but which I 

 regard as one of the most important, is that for the presence of 

 sugar.* For this (as for the testing for albumen) the clear super- 

 natant fluid left after centrifugalization should be used. In health, 

 sugar is present in considerable amount (about o-o6 per cent.), and 

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

 either reduced to a trace or, much more frequently, completely 

 absent. It is not a certain test, but next to the presence of 

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

 meningitis. 



[There are also characteristic chemical changes in uraemia, to 

 which I have paid a good deal of attention. In health the 

 cerebro-spinal fluid contains about 0-035 to 0-04 per cent, of urea, 

 07 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 disturbed, but in uraemia there 

 is abundant evidence of retention of soluble substances. The urea 

 increases greatly — the maximum I have seen being 0-4 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 of such simple constitution as the cerebro-spinal fluid. 

 It is occasionally of value in patients found unconscious. In 

 one such case I was able to exclude uraemia definitely, though 

 the urine contained albumen and casts : it turned out to be a case 



* 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 ofl' from an unconcentrated specimen is 

 soluble in the fluid. 



