842 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
communis per ccm. at the outset of an experiment, was found to be quite 
free from them after one hour’s exposure to direct sunlight. 
The control test showed about the same number of bacteria at the 
beginning and at the end of the experiment. Diffuse daylight was found 
to exert a similar but less powerful influence. 
From the foregoing the following conclusions are drawn : — (1) That 
in experiments as to the behaviour of bacteria in water, the influence of 
sunlight must always be reckoned with, hence most of the earlier obser- 
vations can only be regarded as loosely approximate. (2) That though 
in the natural purification of rivers and lakes other factors may 
play a part, yet the influence of light must be regarded as the most 
important. 
Effect of Ozone on Bacteria.* — Herr Ohlmuller has made some 
experiments with a view of testing the action of ozone on bacteria. In 
the first set, 478*8 mg. ozone mixed with 76 litres of dry air were made 
to pass over dry silk threads which had been previously steeped in a 
two days’ old cultivation of typhoid bacillus. Not the least alteration 
was observed in the vitality of the micro-organisms after an exposure to 
the ozone of one hour. When, however, moist air was used, under 
similar conditions as in the previous experiment, no development of the 
bacilli took place. 
A third experiment was undertaken with the object of ascertaining the 
action of ozone on bacteria adhering to objects in a large space, as in a 
dwelling room. The author came to the conclusion that ozone is not 
suitable for disinfecting either objects or dwelling rooms. 
In the second portion of his work the author deals with the action of 
ozonized air on bacteria in watery fluids, and he found that ozone is 
strongly prejudicial to bacteria suspended in water, provided that the 
water is not too strongly impregnated with lifeless organic matter. The 
result is the same when the quantity of the organic matter is oxidized to 
a certain degree by the ozone. 
Influence of Movement on the Growth and Virulence of Micro- 
organisms.f — Herr Schmidt has made some experiments for the purpose 
of ascertaining the effect of movement on bacteria. The movements 
were effected by means of a shaking apparatus, and partly by hand. 
A loopful of a pure cultivation was mixed with a certain amount of 
tap water or of distilled water, and after the shaking, roll cultivations 
were made from the fluid. The shaking apparatus appeared to exert 
an influence only on the Finkler-Prior bacillus, and once on anthrax, 
though the virulence of the latter was not diminished. Shaking by 
hand quite destroyed the vitality of St. pyogenes citreus , and dimi- 
nished that of all bacteria suspended in tap water, but had not 
any perceptible effect on the bacillus of typhoid. The virulence of 
anthrax was not impaired. The author’s view seems to be that the 
influence of the motion of water in the self-purification of streams 
has been much overrated, although he is inclined to think that the 
pressure from a mass of water might kill single microbes or diminish 
their virulence. 
* Arb. K. Gesundheitsamte, viii. (1892) No. 1. See Centralbl. f. Bakteriol. 
u. Parasitenk., xi. (1892) pp. 773-5. 
f Arch. f. Hygiene, xiii. p. 247. See Centralbl. f. Bakteriol. u. Parasitenk., xi. 
1892) pp. 691-2. 
