DILUTION BOTTLES 3 
with glass stoppers are greatly superior to those requiring cotton stoppers 
but these may be used if the cotton is rolled tightly or contains a cork 
stopper inside of it. Square bottles of the ‘“‘Blake”’’ type holding 
Fig. 2.—Types of Petri Dishes and Other Dishes for Bacteiiological Purposes 
about 200 c.c. are useful and pack together well. If bottles are used for 
dilutions great care must be exercised in sterilization to prevent cracking 
On account of this some laboratories use Florence flasks for holding the 
dilution water. The dilution bottles should be filled with decimal 
quantities of water, Where it is desired to obtain exact quantities 
