

IMPORTANT NEW EXPERIMENTS 137 
To get rid, therefore, of all doubt concerning 
cotton-wool as a protective filter in such experi- 
ments, I determined to repeat the urine and liquor- 
potassze experiments with hermetically sealed vessels 
from which air had been expelled by boiling, and to 
take the further precaution of boiling the liquor- 
potasse tubes before inserting them into the ex- 
perimental vessels. It was safe at once to resort to 
such a method, because I had previously ascertained 
that urine neutralised before boiling would ferment 
in such closed airless vessels almost, though not 
quite, as freely as in flasks plugged with cotton- 
wool. There was, therefore, nothing unduly 
restrictive in the proposed conditions. 
The new mode of procedure which I devised was 
conducted as follows :— 
In the first place a stock of liquor-potassz tubes 
had to be prepared beforehand containing con- 
venient amounts of liquor potassz. Some were 
charged with 8, others with 10, and others with 
12 or more minims. Those containing the same 
quantity were kept together in separate batches 
duly labelled and ready for use, as occasion re- 
quired, according to the degree of acidity of the 
urine with which experiment was .to be made. In 
order to ensure perfect accuracy in the measure- 
ment of the liquor potassee, I made use of a small 
burette-tube (Fig. 3) graduated to minims and fitted 
with a stopcock, with which even half-minims could 
be delivered with ease. 
Having prepared a number of small glass tubes 
closed at one end and drawn out at the other, I 
