Ill] HUMAN BLOOD CORPUSCLES. COUNTING 27 



large square. A large square has an area of y^ sq. mm., the 

 cubic content of the space above it is T ^ 5 cub. mm. Hence the 

 average number found multiplied by 160 gives the number in 

 1 cub. mm. of the diluted blood, and 10 times this is the number 

 in 1 c.mm. of the blood. 



9. If Gower's haemacytometer is used proceed in the following 

 manner. 



Fill the larger pipette with Hayem's or other diluting fluid (cp. 

 Notes) up to the mark on the stem, it then contains 995 c.mm. ; empty 

 it into the measuring glass. Fill the small pipette with freshly drawn 

 blood up to the line marked 5 c.mm. ; empty it into the measuring 

 glass, and with the fluid in the measuring glass wash out the blood 

 sticking to the inside of the tube; thoroughly mix the blood and 

 diluting fluid with the glass spatula, place a small drop of the mixture 

 in the centre of the glass cell and over it lay a cover-slip, arrange the 

 springs on the cover-slip to keep it in position, and under a high 

 power count the number of red corpuscles in ten of the squares which 

 are marked at the bottom of the glass cell. 



Since the depth of the cell is mm. and the side of each square 

 is T Vmm., there is beneath each square -gfo c.mm. of the mixture, i.e. 

 TSTnrfnr c.mm. of blood ; hence the number of corpuscles in 10 squares 

 multiplied by 10,000 gives the number of corpuscles in 1 c.mm. blood. 



DEMONSTRATION. 



Stage for varying temperature of hanging drop, and 

 passing gases over it. 



