16 
Going further, we find by reference to the tables for estimating the 
absolute humidity the weight of vapor in a cubic foot corresponding 
to a temperature of 80° F. and relative humidity of 72 per cent as 
follows : 
Grains. 
At 80° F. and 70 per cent the weight is 7. 654 
The additional weight for 2 per cent is one-tenth the weight for 20 per cent, viz 218 
Hence the weight at 80° F. and 72 per cent is 7. 872 
As it- was desired to know the temperature, relative and absolute 
humidity in our work in the room at certain stages of the experiment, 
and as the presence of the formaldehyde made it impossible to enter 
the room, the psychrometer was used in another way. After the 
handle was removed the psychrometer was fastened to a block of 
wood, which in turn was attached to the end of the shaft of a centri- 
fuge passed through a small hole in one of the doors. By turning the 
crank of the centrifuge on the outside the psychrometer was rapidly 
revolved on the inside of the room. A cup of water was provided on 
the inside, so the wet bulb could be moistened, and a small window in 
the door just under the revolving apparatus made it possible to read 
the registration of the thermometers. By means of this apparatus 
the temperature, humidity, etc., of the room could be determined 
when desired. The results of whirling the psychrometer by this 
method were found on comparison to be practically the same as when 
used by hand. 
%J 
BACTERIOLOGICAL METHODS. 
The nonspore-bearing organisms, Bacillus pyooyaneous , B. coli com- 
munis, B. typhosus , B. dysenterise (Shiga), and B. diphtheria, were 
grown on agar slants at temperature of 37° C. for 24 hours before 
using. 
For spores the B. subtilis was grown on agar slants about 40 days — 
a portion of the time at incubator temperature and the other portion 
at room temperature. 
Different kinds of material were tried for exposing the organisms 
on — such as small pieces of blanket, linen, cotton, silk threads, filter 
paper, and glass — hut it was found that filter paper and glass answered 
the purpose better than the others, and consequently were used 
throughout these experiments. It was foimd that in using a heavy 
material for tins purpose sufficient formaldehyde would at times be 
carried over into the tube of nutrient bouillon in which they were 
planted to inhibit bacterial growth. This was especially so if the 
pieces of material used were of considerable size. 
The slips of filter paper and pieces of glass used were about 0.5 cm. 
square and were sterilized before contaminating with the organism. 
An emulsion of the organism ta be used was made in sterilized water . * 
