August 5, 1886 | 
NATURE 
a9 
phthisis or consumptive diseases has, however, increased 
during the same period, although those of acute bronch- 
itis and pneumonia have decreased. Acute pneumonia 
is now considered by many to be propagated by infection 
from specific organisms occasionally present in the air. 
The curves for the year 1883-84, representing the average 
weekly number of bacteria present in a cubic metre of the 
air of the Rue de Rivoli, A, and the weekly deaths from 
zymotic disease, B, are shown in Fig. 1. The curves are 
seen to present somewhat similar fluctuations except at 
the end of July and the first half of August, when the 
number of bacteria suddenly decrease—owing to the hot 
weather and sustained high temperature—whilst the 
deaths from zymotic disease undergo a large increase, 
owing to excessive mortality from infantile diarrhoea. The 
variations in the number fof bacteria from week to week 
will be seen to be very much larger and more sudden 
than the variations in the zymotic death-rate. Very little 
can be deduced from comparisons extending over one 
year only, and although we are far from asserting that 
there can be no mutual relation between the number of 
micro-organisms present in the air, and the greater or less 
prevalence of epidemic disease among the community 
who breathe such air, still it is unsafe to found any argu- 
ments on such obviously inadequate data. It is only just 
to Dr. Miquel to say here that he recognises these diffi- 
air of the higher mountains an average of only 1 bac- 
terium per cubic metre (Freudenreich). 
A considerable part of the Report is taken up with an 
account of researches conducted by M. Moreau into the 
number of organisms present in sea-air. These investi- 
gations—undertaken under circumstances of consider- 
able difficulty on board ship, and conducted on an 
elaborate scale—are of much interest as bearing on the 
treatment of phthisis by high mountain altitudes or by 
sea voyages—in both cases the special object desired 
being to place the patient in an atmosphere free from all 
impurities. We will quote a few of M. Moreau’s conclu- 
sions on this subject :—(1) Air taken on the coast, when 
the wind is blowing off the sea from a direction in which 
land is at a great distance, is in a state of almost perfect 
purity. (2) In the neighbourhood of continents, winds 
blowing from the land always bring an impure atmo- 
sphere ; at 100 kilometres from the coast this impurity 
has disappeared. (3) During moderate weather the sea 
does not yield to the air any of its contained bacteria ; 
during rough and stormy weather sea-air is charged with 
a minute quantity of bacteria. (4) The air of ships’ 
cabins is also charged with a number of microbes in- 
comparably greater than that of the open air at sea, but 
the purity of the air of these cabins increases rapidly 
during the first days of the voyage; later on, an equili- 
AL 12 
420 1 re 
390} a 11 
360} -+ A 
33° ath 10 
300 i+ -t 
279 9 
240 a 
Ba LN assay tS) 
180 1 } 
ago PN TTS 7 
120 4 
go | 6 
60 
go a re) 
2 LLL | ie 
: al ‘ | 15C. 
Oct. Nov. Dec. |Jan. -|April|) Sam.9 10 411Noontpm.2. 3.4. 5 6 7 ‘] 
1883 1884 
Fic. 1. 
culties, and is rightly cautious in drawing any conclu- 
sions except such as are founded upon an extended series 
of observations. 
At the commencement of June 1884, Dr. Miquel, who 
was then in London, made some observations on the 
number of bacteria contained in the air of Ryder Street, 
St. James’s, A cubic metre of this air was found to con- 
tain only 240 organisms, but this low result was probably 
due to the wet weather which prevailed on four out of 
the five days on which the experiments were conducted 
—the air being remarkably free from dust. In Paris at 
the same time the air of the Rue de Rivoli contained 360 
organisms per cubic metre. Dr. Miquel would not, how- 
ever, be surprised to find that the air of London was 
habitually fairly pure and free from organisms, owing to 
the proximity of the sea, and the fact that the houses of 
London being generally of no great height—unlike Paris— 
the streets are continually being swept by currents of air. 
The air of sleeping-apartments is very impure as regards 
the number of contained micro-organisms. One such 
room in Paris was found to contain on the average in the 
winter and spring of 1882, 73,540 bacteria per cubic 
metre, and the air of the Hdépital de la Pitié has been 
observed to contain 79,000 bacteria per cubic metre. In 
contra-distinction to these large numbers, the air over 
the Atlantic Ocean (Moreau and Miquel) has been found 
to contain from o to 6 bacteria per cubic metre, and the 
Fic. 2. 
brium appears to be established, depending on the amount 
of purification of the air by ventilation and the number 
of occupants. (5) The air of ships’ cabins is relatively 
very poor in bacteria; these probably are one hundred 
times less in number than the air of an occupied room in 
Paris. 
Observations have been made at Montsouris on the 
hourly variations in the number of bacteria contained in 
a cubic metre of air. These observations go to show 
that, contrary to the generally held opinion, the air is less 
pure—7.e. contains larger numbers of bacterla—during the 
morning and evening than at midday. In Fig. 2 are 
shown curves corresponding to proportional figures which 
illustrate this phenomenon, as ascertained by forty ex- 
periments. A is the bacterial curve, T is the curve repre- 
senting the temperature, and Vv is the velocity of the wind. 
The lowest point of the bacterial curve is between noon 
and 1 p.m., two hours before the maximum temperature 
is reached. From $ o’clock in the evening until midnight 
the number of microbes generally remains high, but de- 
creases rapidly from midnight to 3 a.m., two or three 
hours before the lowest temperature is reached, and rises 
rapidly from 4 a.m.—when the ground and vegetation are 
covered with dew—until 6 am., when the maximum is 
reached. These night observations, however, are too 
few in number to be depended upon to give a very correct 
average. Rain, as has been before remarked, rapidly 
