126 
TENTH REPORT. 
• Preparation of Bacterial Vaccines . — A pure culture of the bacteria from which 
the vaccine is to be made is grown on inclined agar for twenty-four hours. 
From 2 to 4 cc. of sterile physiological salt solution is placed in the culture 
tube, and the growth separated from the agar by means of a platinum wire. 
Table II.— Counting the vaccine. p 
'•% 
This chart shows the count of bacteria and of red blood cells in twenty successive fields of the 
microscope and the subsequent computations. 
The number of red cells counted (308) is to the number of bacteria counted (224) as the numoer of 
red cells per cubic centimeter in normal blood (5.000.000.000) is to the number of bacteria per cc. in 
the suspension (3,636,000,000). This count (3.636,000,000) divided by the count desired in the final 
dilution (400,000,000) gives the number of times t (9) this suspension must be diluted to bring it to 
the desired strength. 
