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among the majority of the family. There is therefore, on the facts so far as they could be ascertained,
reason for regarding the eating of watercress as not explicable of the whole of these outbreaks, and if
this position be accepted an additional factor must have been operative having the ability to cause a
number of cases not strikingly less than those which are associated with the eating of watercress. All,
therefore, that can be deduced from Dr. Warry's interesting enquiry is that in this particular outbreak
the incidence of attack upon watercress eaters was greater than would have been anticipated from the
proportion which he found watercress eating families bore to the total families in 124 houses in the
infected area, and indeed Dr. Warry does not himself suggest that the evidence against the watercress
derived from incidence of attack is of a more conclusive nature than that stated.
On making enquiry as to the sources from which the watercress consumed was obtained, it was
ascertained that that eaten by sufferers in the A outbreak had been purchased in twenty-one instances from
hawkers, and in eight instances from a particular shop, while that eaten by sufferers in the B outbreak was
obtained from hawkers in twenty cases, in three cases it came from various sources, and in two others
the source was not known. Dr. Warry states that his suspicion was directed to watercress beds in
West Ham, "as being chiefly concerned in the unusual incidence of enteric fever," and on visiting
these beds he found that they were " fed by almost undiluted sewage." Seventeen samples of
watercress were obtained from various sources in Hackney, and all of these on bacteriological examination
were found to contain bacillus coli.
The question of the risk to health associated with use of raw vegetables and fruit produced on
sewage farms was made the subject of study in 1902, in France, by a Commission (Messieurs Roux,
Ogier and Wurtz), who reported to the Comity Consultatif d'Hygiere Publique. For particulars of this
report I am indebted to Monsieur Masson, of the Prefecture of the Seine. This Commission quoted
experiments made by Messieurs Wurtz and Bourges (Archives de Mudecine Experimentale, July, 1901),
who grew cress, radishes and lettuce in earth watered with cultures of the bacilli of anthrax, enteric
fever, and tubercle. The pathogenic germs in question were found to be present on examination of
portions of the stalk of the plants at a height of even three decimetres (twelve inches) above ground
level. Again, potatoes coated over with anthrax bacilli and planted at a depth of a decimetre were
allowed to sprout, and as long as 101 days afterwards the anthrax organism was recovered from the
stalk of the growing plant. The experimenters note that laboratory conditions may differ from those
existing on the sewage farm; for instance, there is the bactericidal action of sunlight to take into account,
and the cleansing effect of rain. Furthermore, in heavy storms mud may be splashed, as they note,
to quite a remarkable distance above ground level, and so contaminate the stalk or leaves of plants. The
Commission conclude that it is advisable, in the light of their experiments, that the cultivation of
vegetables and fruit intended to be consumed in the raw state should not be allowed upon land fed with
sewage, and that the Paris municipal authority should take steps to have a stipulation to this effect in
contracts entered into in the future with cultivators of such lands.
It is not quite clear whether or not the observations just referred to must be held to indicate that
the bacillus typhosus may grow and multiply in vegetable tissues. If this were proved to be the case
the difficulties which acceptance of Jan hypothesis of watercress causation of enteric fever entails
would be materially lessened. Dr. Houston has carefully considered this matter so far as bacillus coli
is concerned, and has made bacteriological examination of cress after repeated washings. If bacillus
coli multiplied to any great extent within the plant, the number of these organisms in cress grown in
sewage-polluted water ought to have been greater than in corresponding amounts of circumfluent
water. Dr. Houston's results on the whole do not seem to support this hypothesis. Further, on
the foregoing assumption, the number of bacillus coli in initially impure, but well washed cress, should
have been much greater than Dr. Houston's analyses show, as it is inconceivable that his washings
would remove all germs interiorly situated.*
If it be assumed that the cress is a source of danger merely by virtue of the fact that it acts as a
carrier of sewage-contaminated water, it must be admitted to be unlikely that a marked outbreak of
enteric fever due to consumption of polluted cress would occur. In all outbreaks of waterborne
enteric fever which have been made the subject of investigation, only a comparatively small
percentage of those drinking the water have been attacked by the disease, and if cress has been
subjected to preliminary washing, the actual amount of polluted water, consumed by the eater of
the cress, must be very small in comparison with the amount swallowed in the case of a
contaminated drinking water supply. On the other hand, however, the watercress in some instances
grows in water which is very grossly polluted, far more grossly polluted than an ordinary drinking
water supply could be.
With a view to determining the actual conditions under which the watercress sold in London
is grown, the Council's inspectors, Messrs. Harrison, Lewis, Tuck and Williamson, have visited some
120 watercress beds, ranging from less than a quarter of an acre to nearly 40 acres in extent, and comprising
all the known beds within some 50 miles of the county supplying the London market. Samples of the
water were taken in the majority of cases, and these samples have been, on the results of chemical
examination (see Report by the Chemist), divided into four classes. The inspectors have also classified
the beds under four headings, according to the degree to which in their estimation there was risk of
pollution. The following statement gives particulars concerning the beds coming under each of the
four headings, A, B, C, D, of the inspectors' classification. It further shows the group to which the
samples from these beds must be relegated on the result of examination by the chemist, and in the
case of groups B, C, D, the nature of the pollution to which the beds were exposed is also specified,
the particulars for each bed being given on a separate fine.
If the results of Dr. Houston's investigations are accepted as evidence against the multiplication of li. coli in living
cress tissues, it is most unlikely that the less robust and highly specialised B. typhosus would grow and multiply under parallel
conditions. Moreover, it is worth noting that the coli-like microbes isolated from cress and the "washings" of cress were
less typical than tho coli-like microbes isolated from the circumfluent water.
4058] A. 2