48 ROYAL SOCIETY OF CANADA 
When it was desired to make an experiment, the aspirator or pump 
and the lead tubing were first set in their proper positions. The ex- 
perimental and control tubes were taken out of their test tubes and 
attached to the clamp stand as shown in Figs. 1 and 3. A piece of 
rubber tubing on one end of the lead pipe was pushed over the exit 
end of the experimental tube. The cotton wool stoppers, a and b 
in Figs. 1, 2 and 3, at the entrance ends of the two tubes, were pulled 
out and thrown away, whereupon the air was drawn through the 
experimental tube by one or other of the two methods already described. 
As soon as this had been done, the third glass tube was taken out of its 
test tube and its stoppers removed and inserted into the entrance 
ends of the experimental and control tubes respectively. The lead 
pipe was then detached from the experimental tube which was then 
replaced in the sterilised stoppered test tube in which it had been 
transported; the control tube was also replaced in its test tube. The 
two test tubes were then taken into the laboratory. 
For the purpose of cultivating the micro-organisms, three flasks, 
fitted with cotton-wool stoppers, were sterilised in the usual manner. 
One of them was a conical flask of 100 c.c. capacity, and the other two 
were Florence flasks of 250 and 500 c.c. capacity respectively. 
The culture medium was composed of: 
Distilling weet santo TA ee eee tee neat 1000 c.c. 
Taz} 8051090: | Gee Gn aria i eaipr ain,” oD EIMRRRnm cer Sy i 10 gm. 
|= 9150) Re ee I awe Ve YER ST enact 10 gm. 
Liebio meat extract.c: cue) me 3 gm. 
Sodnin-chlarides ne tence let Renters Spee 5 em. 
Gelataiie coos tsar sushi eed as on OS 100 gm. 
This medium, before being cleared with an egg, was neutralised 
in as careful manner as possible, as our preliminary experiments showed 
us that even very slight acidity considerably diminished the number 
of colonies which developed. After the medium had been well mixed, 
neutralization was effected by the well-known phenolphtalein method. 
Fairly large test tubes were nearly filled with the medium, which was 
then sterilised in the usual manner. 
For the purpose of determining the number of micro-organisms 
in the plugs, the medium contained within a test tube was melted by 
means of warm water; about one-half of it was poured into the largest 
flask and the remainder about equally divided between the other two. 
The experimental tube was then removed from its test tube and, 
with the help of a file, broken across in the middle. The cotton wool 
stopper at the entrance end of the tube (Fig. 2, a) was then removed 
and inserted into the newly-made open end of the exit half of the tube, 
