116 
PRINCIPLES OF BACTERIOLOGY 
pus or other infectious material is transferred to Tube 1 
and well mixed by rotating the tube; two loopfuls are 
transferred from Tube 1 to Tube 2, and five loopfuls 
from Tube 2 to Tube 3; in this way the bacterial dilu¬ 
tion is made progressively higher. The contents of each 
tube are then poured into each of three Petri dishes, 
which are numbered to correspond to tubes, and the 
plates are incubated. Next day the separate colonies are 
studied in plate No. 3 (containing the least number of 
colonies), and separate colonies are picked and inocu¬ 
lated on slants, if necessary. 
5. Examination of Peritoneal, Pleural and Pericardial 
Fluids.—These should be first centrifugalized and the 
sediment examined in a smear preparation. Cultures 
may be made either in a liquid medium by adding a 
few cubic centimeters of the material to a tube or a 
flask of the proper medium, or plating on agar. 
6. The examination of cerebrospinal fluid should be 
carried out in the same manner as above. 
7. Urine.—Catheterized specimen of urine should be 
secured, centrifugalized and smears and cultures made in 
the usual way. 
8. Feces is most frequently examined for typhoid 
bacillus: a small piece is emulsified in a test tube of 
sterile physiologic salt solution, and dilutions are made 
into three tubes, as in plating, the contents of each be- 
being poured in Petri dishes containing Endo’s medium; 
next day a colorless colony is picked and transferred to 
Russell’s double sugar agar tube; after twenty-four hours ’ 
incubation if the colony was one of typhoid bacillus, part 
of the tube will have turned red but no gas bubble will 
have formed. (See section on Russell’s Medium under 
Culture Media.) 
9. Blood Culture.—Sterilize the elbow bend with two 
