ESTIMATION OF THE NUMBER OF LEUCOCYTES 215 



You can tell when this has happened by the fact that the ball inside 

 the bulb will emit a clear ringing sound when the pipette is 

 shaken. It is useless to attempt to dry the tube by blowing 

 through it from the mouth. 



If acetone is at hand, it is a good plan to use this fluid instead 

 of alcohol, the use of ether being then unnecessary. Acetone 

 mixes freely with water, and is extremely volatile. The process 

 of cleaning may thus be shortened, one step being omitted. 



If blood has coagulated within the apparatus, it must be 

 digested out. Fill the whole with an artificial digestion fluid 

 (pepsin and very dilute hydrochloric acid), and place it in a 

 test-tube of the same fluid in a warm place for twenty-four hours. 

 Then try to clean it as before, and repeat the digestion if this is 

 impossible. 



Clinical Applications. 



The clinical applications of the leucocyte count are so wide 

 that it is hardly possible to summarize them here ; it is more 

 convenient to refer to each special case separately under the 

 heading of the blood- count as a whole. For example, in dealing 

 with typhoid fever the leucocyte count is explained and the points 

 on which a diagnosis is framed are given, which, in a case in 

 which there is a doubt as to the diagnosis between this con- 

 dition and pneumonia, may be referred to in conjunction with the 

 account of the latter. 



It will be convenient, however, to give a list of the usual 

 counts met with in certain diseases, classified under five headings 

 in respect of the number of leucocytes to be expected in them. 

 But these figures must always be considered with reference to 

 the fuller accounts of the diseases in question. 



I. Enormous Leucocytosis (100,000 to 1,000,000). — Such 

 figures are practically only met with in myelogenous or lymphatic 

 leucocythaemia, though suppuration, pneumonia, and hooping- 

 cough may very rarely approximate thereto. 



II. High Leucocytosis (20,000 to 100,000). — Suppuration in 

 all situations and of all kinds, the degree of the leucocytosis being 

 a measure of the virulence of the organism and the resisting 

 power of the patient. 



Pneumonia, in which the same facts hold. 



Hooping-cough. 



Meningitis, especially suppurative meningitis, whether cerebro- 



