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disease sweating is not a prominent symptom ? A veterinary authority said sweating
was not marked as a rule in any disease in horses. Thereupon it was urged that
in human influenza sweating might be due to want of washing, drugs, etc. (This,
if true of recent influenza, does not readily admit of being substantiated by an
appeal to earlier epidemiological literature.) Anyone who has the curiosity to turn
up Franklin Parsons' Table of Symptoms in the 1889.90 epidemic will, oddly enough,
not find " sweating " there. But in the later report, published in 1893, p. 61, it is
noted that " a peculiar pungent odour was remarked as coming from the sweat of
influenza cases." Of course, it may be said, when writers on epidemiology speak
of sweat in influenza, they have in mind the peculiar pungent odour of influenza
sweats. They are not so much thinking of what has occurred, as of " what has
occurred that in their experience never occurred before." The peculiar pungent
odour, in fact, is again and again encountered in pandemic prevalences. Then in
later epidemics infantile paralysis, ophthalmoplegias, retraction of the head, drowsiness,
myalgia, polyneuritis, each in its turn, becomes the " characteristic pathognomonic
symptom." These, as the epidemiologist knows, are just the phases
of influenza, and it is difficult to see how to analyse them by means of " fourfold
tables." They cannot be envisaged at all unless the enquirer carefully looks for
them, and he must look for some time, for as Sydenham has said, the brief lifetime
of any one physician is barely long enough to enable him to follow the cycles observed
in epidemic diseases.
The great problem of the influenzal group of diseases is the problem of immunity.
In the Ministry of Health report it is sought to supply an answer to the question—
Is immunity against influenza produced by a previous attack of the disease ? To
this question the fourfold table, though with considerable hesitation, replies in the
affirmative. But it must be realised that the verdict cannot really be pronounced
until the preliminary question, What is influenza ?, has been settled. As the
Ministry's report says, " Many of the particulars have been gathered in 14 selected
centres of enquiry by untrained or partly trained observers working often under
pressure, while even for the expert clinician or epidemiologist to decide, upon the
evidence of an uneducated witness, whether he or a member of his family has had an
attack of influenza, is a matter of delicacy. Hence we do not suppose that a high
standard of accuracy has been reached." The difficulties are really even more
fundamental than this. If it be agreed, as most people are agreed nowadays, that
influenza is an endemic disease, it must be realised that the question, whether an
attack of pandemic influenza protects against another, is one that concerns the
succeeding even more than it does the present generation. The latter must look
nearer home and forthwith set about studying the phenomena of immunity in the
case of the diseases of the influenzal group. This is no light task, for the study of
immunity has hitherto been based mainly upon examination of results obtained by
inoculating laboratory animals, and there is danger of ignoring the existence of the
forest of naturally acquired immunity, owing to the extent to which the wood is
hidden by a tangled upgrowth of details relating to artificially acquired immunity.
Naturally acquired immunity, notwithstanding all this, merits careful study.
The veterinarians have long recognised the enhanced value of an animal that has
been " salted " against disease ; just as hospital authorities concerned with smallpox
employ vaccinated staffs, and as in the days when typhus was prevalent, it was
recognised that a special value was attachable to the doctor or nurse who had undergone
attack by the disease. Epidemics of measles or whooping.cough only develop
when there are sufficient numbers of susceptible children to enable them to do so,
and the precise periodicity of recurrences of these epidemic diseases in certain communities,
is mainly determined by the length of the time interval required for the
upgrowth of the new generation of susceptibles. In smallpox, as is clearly shown
by the figures available from Geneva in the 16th.18th centuries, and from Kilmarnock
between 1728 and 1764, from 96 to 99 per cent, of the deaths in pre.vaccination days