CYTODIAGNOSIS 2QQ 



THE MENINGES. 



Here the technique is somewhat different. Clotting is not 

 so likely to occur, and when it does so is much slower, so 

 that if the fluid can be examined in any reasonable time there 

 is no necessity to break up the clot. This is fortunate, since 

 the number of cells present is of importance, and they cannot 

 be counted in a specimen which has coagulated. My own 

 method is to count the cells directly, without concentration 

 and without dilution, in a Thoma-Zeiss counting-chamber, by 

 the method used for the leucocytes and described on p. 248. 

 If the specimen has had time to sediment, shake it thoroughly; 

 then place a loopful or two on the counting-chamber, cover 

 it, g-etting Newton's rings, and allow to settle. Then arrange 

 the microscope so that the diameter of the field is equal to that 

 of eight small squares, and proceed to count the leucocytes on 

 forty or eighty fields ; in the former case the result multiplied 

 by two gives the number of cells per cubic millimetre, whilst 

 if eighty are counted the number is given direct, no calculation 

 being necessary. (There is no dilution of the fluid, and you 

 have counted the actual number in J or i cubic millimetre.) 

 The only difficulty arises if red corpuscles are present; they 

 may be distinguished by being less granular and less refrac- 

 tile than the leucocytes, and are not to be counted. 



The following rules may be taken as approximately correct 

 for the numbers of cells met with in various conditions. In 

 health there may be none, and never more than single figures 

 per cubic millimetre : the average is perhaps one or two. In 

 "aseptic" meningitis i.e., that due to syphilis, or that which 

 occurs in tabes, general paralysis, some forms of herpes, and in 

 almost any chronic organic lesion involving* the meninges 

 the number per cubic millimetre is expressed in two or three 

 figures, and usually ranges between 25 and 200. In the acute 

 stage of infantile paralysis it is about the same. In tuber- 

 culous meningitis the numbers are higher, and range between 

 500 and 1,000, but may go much higher, and in "septic" 

 meningitis, including cerebro-spinal meningitis, the numbers 

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

 thousands. 



