Medical Officers of the Army of India.
arrangements? The fact forms the most damning indictment of these arrange
-ments, and I would be content to rest the case for the prosecution on this alone.
Given a damp polluted soil upon which contaminated urine is, at any rate, con
-stantly deposited, and add to this the faulty latrine system, we have abundant foci
of infection provided before we get to the trenching-ground. Let us, however, look
at what we actually know as regards the biological methods of which an adequate
system of removal must form an integral part. It is proved to demonstration
that where a proper water closet and drainage system is in use, there enteric
fever is enormously reduced, if not altogether abolished.* We may, how
-ever, admit that while the chemical qualities of a sewage effluent can be
controlled by biological methods to any extent and to any desired stand
-ard, yet the evidence, so far available, appears to point to the fact that
in some forms which these methods take, there is no large detention or destruc--
tion of the characteristic flora of sewage. Organisms, not indeed ranked as
pathogenic, if highly suspect—e.g., B. coli,a r e f o u n d i n p r a c t i c a l l y t h e s a m e
abundance in a chemically pure effluent as in the original raw sewage, after
passage through downward filtration beds, or after "contact" in aërating "fil--
ters."† The importance of this fact is not to be underestimated, but it may
be pointed out that the prospects of those methods which include an anaërobic
stage are manifestly brighter than those which rely on "aëration" pure and
simple, and for these reasons. The pathogenic organisms of water-borne diseases
are aërobes, even if we allow them a facultative existence where free oxygen
is at a minimum; they are by far the most fastidious and the least
robust in the struggle for life when confined under the conditions which
obtain in a septic tank or bed, which is swarming with anaërobes, and with sapro--
phytic and putrefactive rivals. We know that even among these latter the tide
of victory rises and falls, with the extermination of the least fit at each stage of
the battle, and these are favoured by all the conditions of a natural habitat. It
must go much harder with a parasite and an aërobe; the absence of free oxygen,
the conditions of temperature and the fluctuations in reaction are inimical to
fastidious parasites, even if they had the field to themselves. The "causæ" of
typhoid and cholera are particularly fastidious in these respects and we know
clinically that both lose infective virulence during their passage through the
human organism, which they only regain after exposure to air; and as they are
believed not to form spores‡, they are deprived of their last chance of survival
until the conditions become more favourable. It is not strange, on the contrary
that B. coli and B. enteriditis sporogenes, which are universally present in the
environment, and which are normal habitants of the intestinal tract where putre
-
* See Boobyer's statistics quoted on p. 120.
†
C l o w e s a n d H o u s t o n : R e p o r t s t o L .
C . C .
‡ S e e M i g u l a : " S y s t e m d e r B a k t e r i e n " 1 9 0 0 .
139