THE EXAMINATION OF THE BLOOD 607 



the main slide. Practice will soon enable one to estimate the size of 

 drop required. 



Use i-in. lens and Xo. 4 eye-piece and focus so that a set of sixteen 

 squares is seen. 



Count the red cells in each square and on two sides of it. 



Count up four sets or more of sixteen scjuares each and divide the 

 stun bv the number in each. 



Thus sixty-four squares contain 768 red cells = 12 in each scjuare. 

 The content of each square is 4o x 2^5 x t\t = 40V0 c.mm. 



Hence one c.mm. of the solution contains 473750 ^ 12 red cells. 



lUit the solution was diluted 100 times with the sodium sulphate 

 solution. 



Hence i c.mm. of blood contains '"" = 4,800,000 red blood 



,, 4COO X 12 



cells. 



For White Cells. 



l\se I per cent, acetic solution and a drop of methj-lene blue. A 

 separate pipette giving a 10 per cent, dilution is better. 



In estimating the Hb. in the Tropics. 



A book \\ith stained papers and corresponding blank blotting 

 papers is used. 



A little of the latter is touched with the blood, and then is matched 

 with the stained paper, which gives the percentage of hb. 



A small book costing 5s. will last five vears. 



TO DEMONSTRATE LIVING MALARIAL PARASITES. 



Take a small drop of blood on centre of cover slip. 



Edge the cover slip with vaseline and place it on a slide. 



Examine middle zone with a T^-'n- objective. 



In the outer zone are rouleaux. 



In the middle zone are single red cells. 



In the central zone very few red cells. 



A dull light is required as corpuscles are colourless. 



The parasite will be seen in a red cell and pigment in the parasite. 



If the field is flooded with light the pigment is still clearly seen, 

 but the granular leucocyte is not clearly seen. 



The parasite shows amoeboid movement ; the males will throw out 

 long pseudopodia which lash the red cells, and eventually become free 

 to enter the female cell. The actual entry has not been witnessed. 



TO STAIN THE MALARIAL PARASITE IN THE BLOOD. 



(i) Leishman's stain is the best. It is polychrome. No fixing is 

 recjuired. 

 The eosin stains the red cells. 



