310
Multiplication of B. Anthracis and Cl. Chauvœi
the temperature requirements for the growth and multiplication of anthrax
bacilli. Viljoen, Curson and Fourie [1928] in South Africa remark that it
is unknown ' whether the anthrax organism can persist only in the spore
form or whether the spores can vegetate under certain favourable conditions
and in this way increase in numbers '. This important point ' has never been
settled by direct experimental evidence'. 'In some parts of Europe, the
organism is believed to be a strict obligatory parasite but this belief is based
purely on circumstantial evidence '. In South Africa, the disease is prevalent
both on wet and on dry pastures so that the moisture content of the soil
appears to have little significance. M'Fadyean [1898] states that, although
the bacillus frequently finds outside the body all the conditions essential for
its multiplication, in temperate climates growth is not likely to make much
headway owing to the temperature not being favourable, to competition
with more rapidly growing organisms and to desiccation.
With regard more specifically to water, Frankland and Ward [1893],
in their Second Report to the Water Research Committee of the Royal Society,
summarize the work of some previous investigators on the viability of anthrax
bacteria in water and state that anthrax spores in sterile or unsterilized water
remain alive for many months at ordinary or low temperatures but are slow-
ly destroyed at 35°C. They themselves found that spores persisted in the
living state for many months and in much larger numbers in sterile river or
lake water than in these waters in the unsterilized state, irrespective of whether
the waters were preserved at 18°-20°C. or at 4°-9°C. In the unsterilized waters,
there was a somewhat rapid and, up to a point, continuous decline in the
number of living spores, so that after the lapse of a few days they were often
no longer recognizable ; an unfavourable effect of temperature (18°-20°C.)
upon survival being particularly noticeable with lake water. Direct (winter)
sunlight had a marked and direct bactericidal effect—due not to the heat
rays but to the light rays—both in sterile and in natural water, the spores
added being killed, often within 84 hours. They also found that, while the
organism does not propagate in sterile distilled water, it can multiply exten-
sively in sterilized city sewage. They were unable to show that B. anthracis
multiplies to any considerable extent in freshly collected river water, steri-
lized by filtration or by heat or in the unsterilized state, unless appreciable
quantities of organic food materials are added and the temperature is above
12°C. Apparently, if anthrax bacteria in the vegetative state are introduced,
they die off within the first day or two or, if conditions are favourable, they
sporulate. All told, there was nothing to support the view that B. anthracis
can live and multiply as does a water bacterium in ordinary water. Szasz
[1914] also, in referring to anthrax arising from pond drinking water, con-
siders that it is not due to actual multiplication of the organism in the water
or its muddy sediment.
As to the viability of anthrax spores under natural conditions, there is
no dispute. Hastings [1923] has recently mentioned the high resistance of
anthrax spores from a natural habitat, as compared with spores from arti-
ficial media ; in this matter he is in agreement with Oppermann [1906]. In
a sample of naturally infected pond water, Hastings found spores to be alive
after 18½ years.