TYPHOID AND COLON BACILLI. 147 
those most commonly employed. In doubtful cases 
a dilution of 1: 100 with a one-hour time-limit is 
recommended. 
(a) Place 9 drops of a twenty-four-hour bouillon 
culture of actively motile typhoid bacilli on separate 
Fic. 82.—Bacillus typhosus, from an agar culture six 
hours old, showing the flagella stained by Lé6ffler’s 
method ; x 1000 (Frankel and Pfeiffer). 
spots on a clean cover-glass. Add 1 drop of serum 
from the blood of the suspected typhoid case,’ mix 
1 The blood may be collected in a capillary tube and after 
coagulation the serum removed; or dried blood may be 
moistened with water and the resulting solution used as 
serum. The latter method, however, does not permit accu- 
rate dilution. Chester and Robin have recently devised a 
pipet for delivering a measured drop of blood, so that dilu- 
