242 CLINICAL BACTERIOLOGY AND HjEMATOLOGY 



is expressed in two or three figures, and usually ranges between 

 50 and 200. In tuberculous meningitis the numbers are higher, and 

 1,000 is perhaps the average, but it may go much higher, and in 

 " septic " meningitis, including cerehvo-spinal meningitis, the numbers 

 are very large, often running into tens or even hundreds of 

 thousands. 



Having counted the leucocytes, proceed to centrifugalize the 

 fluid, and examine films from the deposit by the wet or dry method. 

 The former shows the cells more clearly, and is to be preferred 

 when a cytological examination only is required, as in the diagnosis 

 of tabes or general paralysis. Where bacteria are to be looked 

 for, dried films should be made and stained by Jenner's method, 

 or fixed with perchloride and stained by thionin. Then proceed 

 with the chemical examination of the fluid already described. 



Normal fluid occurs in any nervous disease not attended by an 

 organic lesion of the meninges : deep cerebral tumours, hysteria, 

 deep cerebral haemorrhages, peripheral neuritis, epilepsy, syringo- 

 myelia, etc. 



In cerebral tumour the fluid may be under excessive pressure, so 

 that }t squirts out of the needle ; in such cases there may be great 

 relief to the headache after the withdrawal of a considerable 

 amount of fluid. With a cortical tumour there is usually slight 

 lymphocytosis. According to some writers, the pressure is 

 moderately raised in epilepsy. 



Aseptic meningitis, using the term to indicate that there are no 

 cultivable organisms present, occurs in syphilis, tabes, general 

 paralysis, superficial gummata and other tumours, insular sclerosis, 

 chronic alcoholic meningitis, hypertrophic pachymeningitis, acute softening, 

 some cases of herpes, etc. In these cases we may expect to 

 find a hundred or two leucocytes — practically all of which are 

 lymphocytes — per cubic millimetre. In addition there is usually 

 a slight excess of albumin, and sugar is present, though some- 

 times reduced in amount. 



A slight lymphocytosis, therefore, does not in itself give a clue 

 to the diagnosis unless it rests between two conditions, one of 

 ■which causes lymphocytosis, whilst the other does not. Thus, if 

 the diagnosis is either insular sclerosis or hysteria, the presence 

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

 Similarly in the differential 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 



