ESTIMATION OF THE NUMBER OF LEUCOCYTES Ig5 



The diluting fluid is one which destroys ("lakes") the red 

 corpuscles, but does not injure the leucocytes. It consists of a 

 o'3 or 0'5 solution of acetic acid (glacial) in water ; it is better to 

 add a small quantity of methyl violet or gentian violet, so that the 

 leucocytes are stained and thereby rendered more prominent. 

 This solution is best prepared fresh, or at any rate kept in a well- 

 stoppered bottle. 



The pipette is distinguished from that used for the red corpuscles 

 by its having the number 1 1 above the bulb. This indicates that 

 if blood be sucked up to the mark i below the bulb, and diluting 

 fluid up to the transverse mark above the bulb, the dilution will 

 be I in lo, and so on. 



The blood should be sucked up to the mark i if a great excess 

 of leucocytes is not expected. If the case is one of leucocytosis, 

 a greater dilution is better ; whilst if there is a great excess of 

 leucocytes (such as occurs in severe leucocythaemia), it is best to 

 use the red corpuscles pipette with a dilution of i in loo, but 

 employing the acetic acid diluting fluid. Then proceed to make 

 the preparation, and count by the field method as above. 



Immediately after use the pipettes must be thoroughly cleaned. 

 The fluid which remains in the bulb must be blown out, and for 

 this purpose, as well' as for the subsequent washings, it is an 

 advantage to reverse the position of the indiarubber tube, so that 

 the fluid may be blown out through the upper part of the pipette, 

 this being the wider. The whole pipette must now be filled 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 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 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. 



13—2 



