190 THE MICROSCOPICAL NEWS, 
movement must be progressive, not molecular. Multiplication is 
indicated when granules are united in pairs, or in chains or fila- 
ments ; or when rods are bent at an angle, indicative of fission. 
As to size and form, Nageli says: ‘‘ Granules of different size and 
of a more or less irregular form ought not to be considered as 
belonging to the segmented fungi ; if, on the contrary, the granules 
offer dimensions perfectly equal, and a spherical or oval form, the 
distinction is more uncertain: they may belong to the schizomy- 
cetes or be of inorganic nature.” Whilst Nageli relies mostly upon 
movement asa means of diagnosis, Cohn considers development to 
be the best characteristic. He says: “The globules which divide 
and develop in form of chains are organised beings ; when this 
does not occur we are dealing with pseudobacteria.” 
When we consider the number and variety of minute particles 
that have been found in the atmosphere, such as pollen-grains and 
spores of various kinds, fragments of insects, fibres of cotton, iron 
filings, &c., it would be surprising if the bacteria were absent. 
According to Cohn, Miquel, and others, the smaller forms of the 
Bacteriaceze predominate. 
M. Miquel found in the air of Paris that these organisms con- 
sisted of Micrococcus 93 per cent., Bacillus 5 per cent., and 
Bacterium 2 per cent. They were ten times more abundant in the 
streets of Paris than in the park at Montsouris. The proportion 
varied, however, with the height above the city. When 462 germs 
were found in a cubic metre of air, drawn through the tube of an 
aspirator, at the town hall of the fourth arrondissement, only 28 
were gathered at the top of the Panthéon, and 45 at Montsouris. 
In rain water at the latter place they consisted of Bacillus 63 per 
cent., Micrococcus 28 per cent., and Bacterium 9 per cent. Whereas 
64,000 were found in a cubic litre of rain water, only goo were 
obtained from vapour condensed from the air, the river Seine at 
Asniéres yielded 12,800,000, and the sewage at Clichy more than 
80,000,000. ‘They were least prevalent in winter, their numbers 
rose rapidly in spring, attained a maximum in the beginning of 
summer, and gradually sank in autumn. In hospitals they rose to 
an average of 5,600 per cubic metre of air in summer, and to 
more than 10,000 in autumn. A curve representing the weekly 
mortality in Paris was nearly coincident with one representing the 
number of atmospheric bacteria. Each increase of the latter was 
followed in about eight days by an increase of the deaths from 
contagious and epidemic diseases. 
Although a great advance has been made in the methods of in- 
vestigating these organisms since Leeuwenhoek, towards the end 
of the seventeenth century, first observed the larger forms in putrid 
water, and although extended knowledge has been the result of the 
voluminous literature which has appeared concerning them since 
