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The illness occurred mostly in adults who were off colour for one or two days
with nausea, vomiting, headache, slight rise of temperature and malaise. The
laboratories were exceedingly busy at that period, and were not able to devote
the necessary staff to the investigation of the organism, but I have no doubt
the illness was due to a virus spreading from one person to another.
Colds.
Most people have noticed how frequently they get a cold in the head on
returning from a holiday, especially from one where they have been away from
crowds of people. It is possible that the virus of the common cold gains access
to the lining of the nose and throat because the ordinary bacterial inhabitants
are less in number than usual. It is possible that the bacteria have developed
some defensive mechanism against attacks against themselves by the much
smaller viruses. Still higher in the evolutionary scale are the moulds, which
are tiny plant-like structures, and which can manufacture substances like
penicillin which have a deleterious influence on the growth and multiplication
of certain bacteria. Unicellular organisms like the amoeba can ingest and
absorb the chemicals which make up the bodies of the bacteria. A similar
mechanism exists in the human body in which the white cells of the blood
perform a similar function when we are infected with bacteria. It is tempting
to think that in the battle of the species, the organisms higher in the series
develop defensive mechanisms against the inroads of the organisms lower down,
and that possibly over the millions of years the biological battle has resulted
in an equilibrium so that it may be that the survival of the higher organisms
depends on a balance of activity between the viruses and the bacteria.
Structure of Viruses.
There is some evidence for thinking that the viruses consist of chains of
amino acids assembled in a spiral form, like the coil of a spring with bulges
on the wire every so often throughout its length. Variations can take place
in the amino acids occupying the various positions in the spiral. It may be
that the closely similar or mutant forms of the viruses are merely variants of
amino acids in closely similar positions. It may be that a living cell on the
human body can absorb a certain amount of the virus and in doing so the cell
constituents are modified in some way. The effect of the presence of the virus
lasts throughout a lifetime, thus preventing further inroads of the same virus,
and indeed also of closely similar or related viruses. Hence we get the
phenomenon of vaccination whereby the virus of vaccinia or cow pox whilst
occupying the cells of the body prevents the inroad of the closely related smallpox
virus. Even more curious still are viruses quite different in their construction
and effects which can exclude each other from the human living cell.
Thus the virus in the vaccine of yellow fever will prevent an attack by the
virus of influenza A. This action might explain some curious things, such
as why one child in a family does not get chickenpox or measles at the same
time as the others; why some people get the paralytic form of poliomyelitis,
whereas others do not. Do these exceptions depend on a previous immunising
effect by other viruses, which although they occur in the majority of people
miss a certain small proportion ? A virus can sometimes become active when
it attacks a tissue which ordinarily it would not attack, as when a child gets
respiratory paralysis in poliomyelitis following operation for tonsillectomy, or
where an anti-diphtheria inoculation has possibly been contaminated and a
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