142 DR. A. J. EWART ON THE EVOLUTION OF 
Time. CO, present. O present. O absorbed. 
4 hrs. 077 p.c. 20°4 p.c. 0:04 c.c. 
8 , 10 , 194 ,, 0:14 c.c. 
12 ,, 18 , 16:0 ,, 0:48 c.c. 
12 ,, 175 ,, 164 , 0:44 c.c. 
12 ,, 1-48 ,, 164 ,, 0°44 c.c. 
The same facts are brought out by successive observation 
experiments made upon the respiration of the coloured Bacteria. 
The apparatus used for this purpose is worthy of recommendation 
on account of its extreme simplicity. A small short-necked 
flask has a glass tube ground to fit the neck and projecting for 
some distance into its interior. The flask contains sterilized 
bouillon, and after inoculation is left in an almost horizontal 
position with the mouth elosed by a plug of cotton-wool until 
the Bacteria have developed. 
Sterilized air is then drawn through the flask at short intervals 
of time for an hour or two, and the latter then inverted over Hg, 
covered by a film of water. A sample of the air enclosed can 
be taken directly from the flask and analysed in the Bonnier and 
Maugin's apparatus, by closing the mouth of the flask with the 
finger and immersing it in the eup over the entrance-tube and 
then drawing in a small quantity of gas. A sample at once 
taken and analysed must give the composition of ordinary air. 
Then after a given length of time, by gentle agitation and by 
warming the flask with the hand and allowing it to cool again, 
a complete admixture of the gas in the flask with that in the 
relatively short and broad tube is assured. A sample is n0W 
taken and analysed, and after a further five minutes another 
sample is analysed. The mean of the two analyses, which should 
not vary from one another more than a small fraction of a Pt 
cent., is taken as representing the composition of the air at the 
given time. 
For this purpose fairly old cultures containing an abundance 
of pigment, but in which a portion of the bacterial material 18 
no longer living, were employed. 
