482 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the sewage, the coli group, and numerous peptonising putrefaction bac- 
teria. By cultivation these may be split up into other groups: (i.) the 
typhoid which will grow on agar containing 0*2 per cent, citric acid, 
but not on agar containing 2 per cent, carbonate of soda ; (ii.) the cholera 
vibrios which will grow on agar containing 2 per cent, carbonate of 
soda ; and (iii.) the sewage bacteria which will not grow on agar with 
0 • 2 per cent, citric acid. 
The agar cultures are kept at 30°, and acid or alkaline meat broth 
may also be used at the same temperature. If there should be a small 
number of germs their number should be increased by mixing equal 
volumes of the water and sterilised bouillon and keeping it for 24 hours 
at 30°. Samples should then be tested in acid and alkaline media. If 
there be any clouding, then (i.) growth on alkaline gelatin at 10°-18° C. = 
sewage bacteria ; (ii.) growth on alkaline agar at 30°-37° C. = cadaver 
bacteria ; (iii.j growth on acid gelatin at 20°-22° C. = typhoid bacteria. 
Though the same results may be arrived at by examining the bouillon 
yet the recognition is safer and easier on gelatin or agar surface. 
The next step is to test by plate cultivations ; this will determine 
the species, e.g. typhoid, coli bacteria, vibrios, pyogenic organisms, and 
possibly anthrax. Should a colony be suspected to be typhoid, inocu- 
late on saccharated medium, then there will be development of gas with 
coli organisms but not with typhoid. If there be growth on citric acid 
media, then it is typhoid. If there be growth at room temperature on 
alkaline gelatin then sewage bacteria are present. If at room tempera- 
ture an alkaline cultivation shows no growth, but does on incubation, the 
water is impure from excrement and cadaver bacteria are present. Any 
water which on alkaline gelatin or agar gives colonies is harmful. 
Simple Appliance for Bacteriological Examination of Air.* — Dr. 
P. Miquel describes a very ingenious device for examining air. The 
apparatus consists of a conical flask A (fig. 75), furnished with vertical 
and lateral tubes t, t'. The vertical tube is slightly constricted, and in it 
are placed two cotton-wool wads, b , b', the latter lying against the con- 
stricted neck, and being intended to catch any germs which may have 
escaped through the medium. In the lateral tube t' is fitted a thin 
glass rod (“ pointe de verre ”) kept in position in t' by means of a cork 
or caoutchouc plug. The diameter of the pointed glass rod used for 
flasks of 7-8 cm. at the base, varies from 1 to 2 mm. The flasks are 
prepared for use by first inserting the cotton-wool plugs, and then 
pouring in as much gelatin as will suffice, when the flask is slightly 
inclined, to cover the rod, except at the end furthest from t'. The 
vessels are then sterilised for half an hour at 110°. When the apparatus 
is removed from the autoclave, the flasks are tilted so that the tip of 
the glass rod just projects above the level of the gelatin. In this 
position it is left until the gelatin is set. 
When the apparatus is used, it is clamped to a support (fig. 7 6, B) the 
tube t' being directed downwards. To the tube t is fixed a caoutchouc 
tube in connection with an aspirator. The glass rod is now withdrawn, 
and this is effected by first gently warming the plug which supports it 
in the tube t\ and carefully pulling it out, giving it at the same time a 
* Ann. de Microgr., vii. (1895) pp. 103-9 (2 figs.). 
