276 The Phagocytic Power of the Blood 



future manipulations are made easy, because one first makes 

 his suspension, then enumerates the bacteria, and having 

 determined their number, immediately arrives at the 

 appropriate concentration by dilution (Fig. 79). 



Fig. 80. The nephelometer; an instrument used for standardizing 

 bacterial suspensions used for the opsonic test or for vaccines, by com- 

 parison with precipitate of barium sulphate. 



The writer* believes that equally accurate results can be 

 attained by means of a simple instrument which he has 

 called a " nephelometer" (Fig. 80). By the use of this 



Fig. 81. Collecting blood for corpuscles (Miller ). 



instrument one arrives at the appropriate dilution of the 



bacterial suspension by comparison with a tube containing 



* "Jour. Amer. Med. Assoc.," Oct. 5, 1907, xux, p. 1176. 



