PLATINUM WIRES 7 
to clothing, etc. The oxygen which is formed is available for the oxida- 
tion of any reduced substance. 
Platinum Wires. Platinum wires have extended use in bacteriology. 
Different sizes may be used but gauge No. 26 yields the best results. 
A heavier wire requires a longer time for cooling after it has been ster- 
ilized in the flame. A lighter wire may be too flexible. 
In many cases standardized loops are required which deliver the 
same amount of liquid. Instances are the standardization of disin- 
fectants and determination of bacteria in feces according to the Eberle- 
Klien method. St. John (1914) devised a ‘‘loop’’ which gave drops 
of from 0.019 to 0.021 gm. according to the angle at which it was taken 
from the fluid. Under more unfavorable circumstances the variation 
CQ 
Fic. 5.—Types of Holders for Inoculating Needles and Loops. 
A, Special Aluminum and Wooden Handle; B, Aluminum Rod; C, Glass Rod with Fused Wire. 
was from 0.017 to 0.028 gm. The size of the drop cariied by this loop 
is about 0.020 c.c. 
Baskets. These should be made of wire with a mesh small enough 
to retain most of the test tubes used in a laboratory. Any special 
shape or size may be made at the average tin shop. 
GENERAL TECHNIQUE 
Isolation of Microorganisms. This necessitates the plating of 
bacteria in decimal dilutions on solid media. Agar or gelatin may 
be used but the latter gives more data. Ifthe organism which is sought 
in pure culture is known to be mixed with other forms, greater care 
must be exercised. The plating of decimal dilutions is advisable, 
especially where little is known with regard to the number of cells which 
are present. All apparatus must be sterile. Where careful work is 
