150 BLOOD. 



Enumeration of White Blood Cells. 



Use the Thoma-Zeiss instrument with a special pipette. 



Dilute the blood to 10 or 5 pc< in the same manner as for 

 the red cells but with 0*3 pc - solution glacial acetic acid, and 

 proceed as before. 1 p<c> dilution will answer if the white 

 cells are very numerous, provided many fields of 16 squares 

 are counted. 0-6 p-c - NaCl solution coloured with gentian violet 

 may then be used as a diluent. 



Enumeration of Blood Platelets. Use the same instru- 

 ment and dilute the blood with Bizzozzero's fluid (methyl violet 

 1 in 5,000 of normal saline) to 0-5 p - c - 



The operation must be carried out quickly, as the platelets 

 tend to adhere to the glass surfaces and to each other. They 

 must be carefully sought for. Film preparations show them best. 



Estimation of Haemoglobin. (Blood contains normally 

 from 13 to 14 p - c -) 



Gower's Instrument is composed of : 



1. Standard colour tube of the tint of a 1 p - c - solution of 



normal blood. 



2. Graduated tube for diluting blood. 



3. Block for supporting these side by side. 



4. A 20 cubic millimetre pipette. 

 Process : 



Place a drop of distilled water in (2). 



Fill (4) up to the mark with blood, wipe the point, and expel 



the contents into (2). 

 Add distilled water to this drop by drop, with agitation, until 



a tint exactly matching that of the standard is obtained. 



According to the dilution required so is the quantity of 



HbO 9 . If the desired tint is obtained when the fluid in the 



