‘ 
520 
temperature of 35° C. If five or six groups of 
experiments are made in the same day and 
place, the results are almost identical, pro- 
vided that the force and direction of the wind 
are constant, and, above all, if the air has not 
been purified by rain or snow. From this, the 
equal distribution of spores is proved, and not 
that they are in so-called ‘ clouds,’ as has been 
maintained by Tyndall. 
Signs of germination may appear within 
twenty-four hours; but it is usually from the 
second to fourth day that the greatest number 
of flasks are altered. From this time there 
is arapid decrease until the thirtieth day, after 
which any alteration rarely takes place. The 
growth is manifest to the unaided eye in three 
different ways :— 
1°. The liquid preserves its clearness, but a 
more or less voluminous deposit occurs at the 
lower part. 
2°. The liquid is uniformly clouded at first, 
and then a veil arises, or a deposit is formed. 
3°. The liquid remains transparent, but little 
isolated white clouds of silky mycelium appear, 
which can invade the entire fluid. These are 
usually fungous growths, but there are sever- 
al filamentous microbia which can give rise to 
the same appearance. 
In the flasks which are altered by these aerian 
spores, there rarely is perceived that nauseating 
cadaveric odor of intense putrefaction, pro- 
duced by inoculating a drop of water from a 
sewer or even from the Seine. The bacteria 
of the air are only feeble and superficial pu- 
trefactors, and rarely cause a profound decom- 
position of the liquids into which they are 
introduced. It is necessary to banish from 
the mind the idea that we live literally besieged 
by organisms always ready to sow putrefaction 
on the mucous tract of our economies. The 
inhabitants of the country, more privileged in 
this respect than the dwellers in the city, hardly 
introduce into their lungs, in the course of a 
day, one germ of putrid fermentation. 
The degree of alterability of the nutritive 
liquid should always be taken into account in 
experiments ; and numerous investigations were 
made on this point. From these it appeared 
that an infusion of hay was the least suscepti- 
ble of alteration, while neutral beef-bouillon, 
with the addition of one per cent of salt, was 
the most so. Normal urine held a middle place. 
These had been sterilized by boiling for two 
hours at 110° C. Contrary to general expec- 
tation, egg-albumen, diluted with water and 
sterilized by filtration through plaster, was 
found to be almost as resistant as the infusion 
of hay. 
SCIENCE. 
[Vox. IIL, No. 64. 
In order to cultivate the bacteria ina state of 
purity, a drop of one cultivation is transferred 
to another sterilized flask on the point of a 
‘fired’? platinum needle. ‘The danger of in- 
fection from the air, during the time the flasks 
are opened to permit the transfer, is very much 
less than is generally supposed. By computa- 
tion, the chances are only as 1 to 1,500. 
The results of the daily examination of the 
air at Montsouris during three years showed 
that bacteria and their spores were more abun- 
dant during hot weather than cool, and were 
inversely proportional to the degree of moist- 
ure. The direction of the wind was also of 
consequence, that which had traversed Paris 
being richer than that coming from over the 
country. . 
In respect to the seasons, the greatest num- 
ber of germs were found during the autumn, 
then followed summer and spring, and lastly 
came winter, as the following table shows : — 
Autumn, 121 spores per cubic metre of air. 
~! . 66 66 66 ‘ 6 ‘ 
Ulan, Oe 66 (73 66 ” 66 : 
SIVAN B 66 ce 66 (a5 66 66 
Winter, 53 
OrameanofSi ‘ 6c ‘ 66 PONG 
The germs which thus find their way into the 
air are either carried there when dry, or are 
taken up with fine particles of water by the 
wind: they never pass off with the insensible 
evaporation of a fluid. A series of ingenious 
experiments with the condensations from putre- 
fying liquids and substances proved the truth 
of this assertion. 
The comparative analysis of the air taken 
from the streets near the centre of Paris showed 
that it was nine or ten times richer in schizo- 
phytes than that from the Montsouris Park. 
In regard to the relation of the bacteria in 
the air, and the occurrence of epidemics of 
disease, the fact was observed, that, at the time 
when there was a comparative increase of 
deaths from zymotic disease, there was an un- 
usually large number of germs in the air. As 
it is impossible at present to distinguish harm- 
less from pathogenic microbia, and as the inocu- 
lation of cultures from atmospheric spores gave 
nearly negative results, the author wisely does 
not lay great stress upon this coincidence. 
The interiors of houses were next made the 
subject of investigation. It was found, that, 
in a room which was perfectly still and undis- 
turbed, there were 27 microbia to the cubic 
metre, against 97 in the air outside. The num- 
ber in the same space in the author’s labora- 
tory was found to be 215 in 1880, 348 in 1881, 
and 550 in 1882. In an ordinary bed-chamber 
