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active, flying in and out of and about living rooms, and alighting upon food materials, and yet at this
time the diarrhœal prevalence of the year was practically at an end.*
(d) Some further considerations.—A study of typhoid fever and diarrhoea prevalences in the
light of a hypothesis which attributes their spread to one and the same carrier, the fly, raises
further questions. In the first place—Does heavy incidence of the one disease, upon a locality, imply
a like incidence, in one or more years, of the other disease ? Sir George Buchanan investigated
this point in certain English towns more than forty years ago, and concluded that, while some
correspondences were noted, " there remain sufficiently obvious differences between the fluctuations
of mortality from typhoid and from diarrhoea to make it probable that other influences than those
affecting fever have operated on the prevalence of epidemic diarrhoea." Dr. Niven (Annual report,
1894) wrote in a similar sense, saying : " The causes of typhoid fever are, in fact, much more complex
than those of summer diarrhoea." Later (Annual report, 1898), he suggested that possibly midden
privies operated prejudicially in Manchester in promoting both typhoid and diarrhoea prevalences,
but he added " other influences besides that of local filth conditions " enter very largely into the
causation of high mortality from diarrhoea. Dr. Newsholme (Public Health, December, 1899) pointed
out that the table of the Registrar-General, giving average death-rates for diarrhoea and typhoid
fever 1888-1897, shows that there is no necessary association in the positions of towns in respect of
high or low mortality from these diseases. He says: " Sunderland is worst (thirty-third) in the
list for fever, only twenty-third for diarrhoea ; Swansea is thirteenth for fever, third for diarrhoea;
Brighton is second best for fever, only eighth among thirty-three towns for diarrhoea," and so on.
Reference to the corresponding table relating to the last ten years reveals similar discrepancies. If
the fly play an important part in determining prevalence of the two diseases, exceptions such as
are here in question need explanation.
Then, in the second place, question arises as to the association of diarrhoea and typhoid fever
with faulty systems of excrement disposal. Dr. Longstaff, in 1880, said: " We may dismiss as
untenable " the theory that the disease (diarrhoea) is due to filthy privies, for they " are as common
or commoner in the country than in the large towns, and are, therefore, not likely to be the cause
of a town disease." Again, Sir George Buchanan, in 1888, commented upon the maintenance of
the death rate from diarrhoea " after years of sanitary work in England." On the other hand, several
observers have inclined to an opposite view, and Dr. Boobbyer, of Nottingham, has in recent reports
repeatedly urged that privies favour the spread of both diseases. The suggestion has been made
that inquiry as to diarrhoea in relation to flies is likely to be more profitably pursued in towns in which
the dry method of disposal of excreta is still in operation than it is ir London or any other well
drained and sewered town. It is, however, noteworthy that in the poorer parts of towns provided
with water-carriage removal, high rates of diarrhoea mortality still prevail; moreover, while the
contrast between town and country is now far more marked than it was thirty years ago the disease
remains pre-eminently one of large urban communities.
As regards diarrhoea, a further question arises. There is good reason for thinking that maternal
neglect plays an exceedingly important part here. It is true that many " diarrhœal towns " have
faulty systems, of excrement disposal, or contain exceptionally poverty-stricken populations. But
among possible influences that of employment of married women away from home unmistakably
emerges on careful study of the figures!. What bearing has this fact upon the fly hypothesis ? On
the one hand it may be argued that domestic neglect is particularly likely to afford scope for the fly.
On the other, as Dr. Ballard insisted, the question of such neglect, with other influences of urban conditions,
while most marked in diarrhoea, is "noticed also in respect of infant mortality from other
causes." Mr. Foulerton, in a recent report (1908-9), indeed, argues that" the insanitary circumstances
which, in the case of artificially fed children, increase the liability to death during the
summer months, from a diarrhoea resulting from bacterial infection of food, will, in the months of the
year when climate influences favour the development of pneumonia, provide the opportunity for
effective bacterial invasion of the lungs." As Dr. Longstaff has said, "the lungs are susceptible in cold
weather and the intestine in hot." But if bacterial invasion can be accomplished in winter without
the assistance of the fly, why not in summer also? However this may be, it becomes clear that a high
death-rate from diarrhoea may be favoured by many influences which have no necessary dependence
upon the existence of large opportunities for the spread of infection. The death-rate is thus a very rough
and unreliable test of the incidence of the disease. The ordinary difficulties encountered in comparing
death-rates, are further aggravated in the case of diarrhoea by the fact that, while the very young and
the very old contribute most largely to the deaths, the disease itself is not limited to the extremes
of life. This last named consideration especially emphasises the value of notification.
* Dr. Nash refers in the same paper (p. 159) to two outbreaks, one of dysentery and one of typhoid fever,
which had been attributed to flies bred in deposits of house refuse, and, he argues, in support of this view, that there
might have been dysenteric polluted matter at one side of the dust heap and typhoid material at the opposite side.
The difficulty which presents itself with regard to this thesis is that of explaining why all the flics carrying typhoid
material travelled north-east, and all those carrying dysenteric material north-west; the respective fly swarms making
for separate destinations nearly half a mile apart, and dysentery-laden flies invariably choosing the one, and typhoidladen
flies the other destination.
† Miss Collet (Journal of the Royal Statistical Society, 1898) has pointed out that poverty, as gauged by a
domestic servant test, follows, as a rule, high percentage of employment of married women in factories ; and hence
the difficulty of separating the one influence from tho other is great. There is, however, doubt as to how far the
domestic servant test can be relied upon, in a comparison made between a number of towns, including Lancashire
and Yorkshire towns, and also towns in the Midlands ard South of England.