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33
Report of the County Medical Officer—General.
we may occasionally have a relatively high bile-salt-agar count when the evidence is against the water
being seriously if at all polluted.'' In so far, on the other hand, as the bile-salt agar test is to be trusted,
and in so far as reliance is to be placed on the kind of impurity observed as a measure of risk, the results
show that during August and September, the danger incurred is far higher than at other time
If due allowance is made for period of storage before consumption of the water and for period of incubation
of the disease, this finding might even be held by an enthusiastic " water theorist" to be
suggestive, for the maximum prevalence of typhoid fever is apt to occur about six or eight weeks after
the period of maximum impurity.
These considerations make it clear that it is not safe to rely upon averages taken over a whole
year. It cannot reasonably be assumed, because absence of the typhoid bacillus can be inferred from
9 c.c. or 17 c.c. (see Table 4 already referred to), when a whole year is taken into account, that the
absence of a typhoid bacillus can be inferred from these amounts of water at times shortly preceding the
period of special typhoid prevalence. It is, in point of fact, possible that, at such times, absence of
the typhoid bacillus from far smaller amounts of water only can safely be inferred.
The points raised by Dr. Houston's inquiries are both interesting and suggestive, but
clearly the most striking result of his investigations is the demonstration in the water examined of
bacilli indistinguishable from typhoid bacilli. He speaks of them, it is true (on p. 6 of his Report)
as the two "query typhoid" microbes, but, he adds, "If they had been isolated from the blood or
excretions of a patient suffering from typhoid fever they would, I think, have been classed as
typhoid bacilli, as the matter stands all that can be said is that they were practically indistinguishable,
according to my tests, from this microbe."
It is interesting to contrast this cautious attitude of mind with the much more positive conclusions
bacteriologists were prepared to draw as recently as nine years ago from, bacteriologically speaking,
somewhat similar findings. Just after the outbreak of typhoid fever in Lincoln in 1905, the official
report on the outbreak records that "search was made for the bacillus typhosus in the water of the
public supply ; and from a sample taken from one of the sources of this supply on February 1st, a microorganism
was recovered which resembled the bacillus typhosus in all essential respects. A similar
micro-organism which was regarded as possibly being the bacillus typhosus,somewhat altered in character
by sojourn in the water, was isolated from a sample of sediment taken from the 'pure water tank '
which receives the water after filtration at the waterworks on February 11th."
The evidence, apart from that furnished by bacteriological inquiry, afforded "ground for presumption
that the public water supply of the Corporation of Lincoln was concerned in the dissemination
of the fever. " The two positive bacteriological findings were, however, held to determine the matter at
Lincoln. It may be argued, of course, that at Lincoln there was an outburst, in London the typhoid
fever incidence was scattered both in place and in time. In other words the results of the bacteriological
examination must be weighed with the other evidence, but when it is realised that Dr. Houston
evidently attaches no great importance to his two positive results the conclusion follows that if these
results can be almost dismissed from consideration in London, too great significance must not be
attached to similar findings elsewhere. In the last nine or ten years a good deal of time has been devoted
in Germany, in America and in this country to examination of organisms isolated from public water
supplies presenting greater or less resemblance to typhoid bacilli. The odd thing has been that in several
cases in which it has been declared that the typhoid organism had been isolated, the water was doing no
harm, e.g., in a case reported in Germany by Beck and Ohlmiiller and in that of the Belfast water supplly
in 1907. The suspected cultures from Belfast were exhaustively reported upon by Drs. Houston and
Gordon, who concluded that implicit reliance could not be placed upon the agglutination test and they
added that they could not associate a microbe causally with disease in man "even though a certain number
of the tests beside the agglutination test may lend support to the hypothesis of pathogenicity." '
Dr. Houston's more recent and very elaborate study of Thames water carries the matter, a step
further for he has now demonstrated on two separate occasions the presence of microbes indistinguishable
by his most rigorous tests from the typhoid bacillus, and as this result has been obtained by examination
of only two or three dozen gallons of raw water, it is clear that the entire London water supply
may at times contain large numbers of such bacilli. And yet no one is disposed to suggest that London
drinking water seriously contributes to the amount of typhoid fever in London.
But over and above the two positive findings there stands out plainly the consideration of far
greater significance, that proper regard must be paid to the limitations of bacteriology in dealing with
this question. Dr. Houston's reports have brought home to all who have studied them the fact that
failure to demonstrate the presence of the typhoid bacillus in a particular specimen of water does not
necessarily justify the conclusion that the bacillus is not there.
In point of fact the inference that is forced upon the mind is practically similar to that which
must be drawn from the German work referred to in last year's report. When study of bacillus carriers
was first undertaken it was thought that the existence of the bacillus carrying propensity must necessarily
mean infection of those with whom the bacillus carrier came into contact. In last year's report
some of the difficulties which have to be encountered by the upholder of this hypothesis were enumerated
and discussed. Similarly it has been assumed that the presence of a bacillus indistinguishable from
the typhoid bacillus in a public water supply necessarily implies grave danger, but here again the results
do not bear out the surmise. Those who accept the contact theory are compelled to resort to the view
that the carrier's bacilli do not always cause harm, but only do so on the rare occasions (in the life of
many carriers, at any rate, such occasions never occur) when the carrier becomes effective. Similarly,
study of the bacteriology of water compels the bacteriologist, who maintains that the bacillus typhosus
is the causal organism of typhoid fever, to assume either that something must be conjoined with this
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