ESTIMATION OF THE NUMBER OF LEUCOCYTES 251 



with water (preferably distilled), and the water blown out. 

 This process is repeated, using absolute alcohol, and allowing 

 it to run out of the pipette without blowing it. Lastly, fill the 

 whole pipette with ether, remove the indiarubber tube, replace 

 it with the tube of an ordinary spray (such as is used for scent 

 fountains, throat sprays, etc.), and pump air through until the 

 apparatus is absolutely dry. You can tell when this has hap- 

 pened 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 deal- 

 ing 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 condition and pneumonia, may be referred to in conjunc- 

 tion 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 head- 

 ing's 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 lym- 

 phatic leucocythaemia, though suppuration, pneumonia, and 

 hooping-cough may very rarely approximate thereto. 



