HISTOLOGJ. 51 



been diluted and since the squares are only one-tenth 

 of a m.m. square. The average number of red cells 

 is about 5,000,000 in each c.m. of blood in men, and 

 4,500,000 in women. 



Exercise No. 32. Use the Haemoglobinometer. 



1. Take the instrument and set it up in front of a 

 piece of white paper. 



2. Obtain 20 c.m. of blood and place it in the tube 

 provided for the reception of the blood. 



3. Dilute the blood with water until the blood mix- 

 ture and the standard mixture in the tube coincide in 

 color. 



If the blood has the required amount of haemoglobin 

 in it, when you have added the water up to the gradu- 

 ate 100, the two colors will coincide. If it reaches the 

 color before the required amount of w&ter has been 

 added, there is not enough haemoglobin in the speci- 

 men ; and if it requires more water than the 100, there 

 is too much haemoglobin. 



Exercise No. 33. Use the Haematokrit. 



I. Set up the centrifuge and place the Haematokrit 

 in place; revolve the centrifuge very rapidly for three 

 minutes. 



