ESTIMATION OF RED CORPUSCLES. I45 
PROCESS. 
1. Pricking the patient—The blood may be procured 
from the convex border of the lobe of the ear or from 
the lateral surface of the last phalanx of the finger. 
The advantage of the former situation is that the pain 
is very slight, the skin being thin, and that the patient 
cannot see what you are doing and is not likely to start 
at the critical moment. It is to be recommended for 
children and nervous women. The advantage of the 
finger is that the skin is free from hairs, and these are 
objectionable in the preparation of film preparations by 
the cover-glass method; an additional advantage is that 
the patient can put his hand into the position most 
convenient to you and you have not to lean over him. 
The area of the skin to be punctured is washed 
with soap and water and then with pure water, and 
wiped dry. No other sterilisation is necessary unless 
you are also taking blood for bacteriological purposes. 
The needle is sterilised by being passed slowly through 
the flame of a spirit lamp or Bunsen’s burner; the area 
of skin to be pricked is taken between the finger and 
thumb of the left hand, and a rapid and fairly deep stab 
made with the needle. The skin is then released and a 
drop of blood allowed to exude; this is wiped away and 
the next drop which oozes out is used for examination. 
The skin must never be pinched when blood is being 
withdrawn; the blood must always be allowed to flow 
out naturally. 
2. Filling the pipette—The degree of dilution is deter- 
mined by the number of corpuscles per cubic millimetre 
which you expect to find. If the patient is anaemic use 
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