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grounds to be the Bacillus typhosus of Eberth and Gaffky, passes from the body with the
feces, and that the excreta of typhoid patients constitute the main channel of infection
in this disease. The disinfection of such excreta is a matter of extreme difficulty, and is as a rule
very imperfectly carried out even in our fever hospitals. It hence results that sewage becomes a
very important agent in the dissemination of the disease, and contamination of water supplies by
sewage, the chief cause of typhoid epidemics. Our attention in the inquiry which we have carried
out was therefore specially directed to the possible occurrence of the bacillus typhosus in London
sewage, and every colony which seemed likely to belong to this species was the subject of careful
investigation. It has been already mentioned that Bacillus coli communis, a normal inhabitant
of the digestive tract of man and animals, and one of the commonest and most constant
organisms present in sewage, bears a strong resemblance to the typhoid bacillus, and is in
morphological and cultural characters closely allied to it. It can, however, be distinguished
from it readily enough by certain chemical tests, and for the right understanding of the
methods we have employed in searching for it, it is needful to go into this matter in some
detail. In cultural characters, i.e. mode of growth on different nutrient media, the two organisms
resemble one another so closely that even the most experienced bacteriologists would hesitate to
diagnose one from the other by such means alone. In morphological characters they are better to
be distinguished ; the colon bacillus is shorter, and, owing to the possession of fewer flagella, is much
less actively motile. Reliance is, however, chiefly to be placed in their different chemical reactions. The
colon bacillus, when inoculated into sterilized milk and incubated at 37° C. produces coagulation of the
milk in 24 to 36 hours ; the typhoid bacillus has no such power, the milk remaining fluid for an indefinite
period. The colon bacillus, when inoculated into nutrient gelatine, which is then liquefied at 25° C.
and shaken so as to diffuse the bacillus throughout the mass of the nutrient medium, and then allowed
again to solidify and incubated at 22° C., produces abundant gas bubbles as it grows, the typhoid
bacillus under similar conditions produces no gas. The colon bacillus when grown in alkaline beef,
broth, or in peptone solution, at 37° C. produces a body, probably indol, recognised by the development
of a deep red colour on the addition of nitrous acid; the typhoid bacillus has no such power. These
three tests form then an easy means of distinguishing the two organisms, and it may be affirmed that
any given organism which in cultural characters resembles the bacillus typhosus, which is actively
motile and grows into threads longer than those seen in B. coli communis, and which fails to produce
coagulation in milk to form gas bubbles in gelatine shake preparations, and to give rise to indol in
broth or peptone cultures, is at least indistinguishable from the typhoid bacillus, and may with every
degree of probability be regarded as such. Further than this it is impossible to go; the lower animals
do not, so far as we know, suffer from typhoid fever in the sense in which we recognise it in man, and
hence inoculation experiments on animals do not help us to prove a given organism to be the actual
virus of typhoid fever.
With these considerations clearly in view, we proceeded from the outset of our investigations to
scrutinize carefully every colony which in any way seemed to resemble the typhoid bacillus. And in
every case we failed to recognise it. We then became oppressed by a sense of mathematical improbability.
The average amount of sewage produced in London amounts to 200 million gallons per diem.
During June, 1894, 177 cases of typhoid fever were notified in London, to which may be added 13 cases
of continued fever. Assuming each case to last a month, it may be supposed that during the early
summer months, when typhoid is by no means prevalent, two hundred cases of the disease would
represent a fair average of the number existing in London at any one time. A large number of these
cases suffer from constipation and hence contribute very little fecal matter to the general mass of
sewage. Those who suffer from diarrhoea do so, as a rule, only for a certain portion of the time they
are ill. Moreover, it must be remembered that in all outbreaks of typhoid a large number of cases of
diarrhoea occurs, which, though not presenting the typical features of the disease, are probably truly
typhoid in nature, and are capable of disseminating the infection. Any estimate, therefore, of the average
amount of sewage contributed daily by the cases of typhoid in London must be purely conjectural,
but a reasonable estimate of such average amount appears to us to be 1/25000 part of whole, and it
must not be forgotten that every endeavour is made to disinfect this. The mathematical chances of
detecting the typhoid bacillus in ordinary London sewage are therefore extremely remote. If the above
assumption be correct, and if all the typhoid sewage be further assumed to be intimately mixed with
the ordinary sewage, there would only be on an average one typhoid bacillus in every 1/10 c.c. of sewage
at the outfalls. But the largest amount of undiluted sewage with which we have found it possible to
work is 1/5000 of a.c.c., and this only when 90 per cent. of the organisms present were inhibited by the
addition of 0.05 per cent. carbolic acid, and incubation at 37° C.
Discouraged by these considerations we determined to search for the typhoid bacillus in sewers
where it might be expected to be present in larger proportion. To this end we considered the different
fever hospitals, and selected the Eastern Hospital at Homerton as likely to serve our purpose, since it has new
drains easily accessible at the different manholes and inspection chambers, and since also the typhoid
fever cases are located in a separate block of buildings. Having obtained the consent of the
Metropolitan Asylums Board, we entered into correspondence with the resident medical superintendent,
who kindly lent us all the aid in his power. It was agreed that no disinfection of the typhoid stools
should take place for two days preceding our visit, and this was carried out. On the morning of May
23rd we visited the hospital at Homerton. There were at the time some 40 cases of typhoid in the
block set apart for that disease, many being acute cases suffering from diarrhoea. The drain from the
typhoid fever block joins that from the scarlet fever block, and is accessible by a manhole before it
leaves the hospital. At this manhole we collected the sewage in a sterilized bottle, taking small
samples at short intervals, so as to get a fair average specimen. It was unfortunately a wet day, so
that the sewage was considerably diluted, and it contained also a large quantity of soapsuds.
We returned immediately to the laboratory and at once proceeded to make cultivations from