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a well-known proprietary disinfectant, and thus serve to introduce
organic matter into the test of its germicidal value. The experiment
appealed to me as possessing a real practical value. The result was
that the carbolic acid co-efficient of the disinfectant in question was
reduced 40 per cent, below the advertised figure, which is based upon
a naked germ test.
The disinfection of school books is also much neglected. Yet
they may be considerable factors in the transmission of infection,
for all we know to the contrary. This is an item upon which more
work is necessary; but the experiments hitherto performed indicate
that, except when books are markedly soiled, they do not offer favourable
conditions for the retention of germ life. By steeping the most
soiled parts of library books for twenty-four hours in a physiological
solution of salt, and rubbing the binding with the same, the centrifugalized
washings were capable of communicating tubercle to 35
per cent, of 43 guinea-pigs, whereas negative results were obtained
from the cleaner books (Mitelesen and Knopf, in Berlin). The
usual cupboard compartment, in which books are so disposed on
shelves of perforated zinc gauze, that the pages (more especially the
dirty ones) open out, or in which the books are suspended upon
wires from the top of the chamber, fumigated with formic aldehyde
for two or three hours, appears to be satisfactory; but if the book
is an old and markedly soiled one, I believe that we should always
recommend its destruction. Probably this method is as satisfactory
in practice as that recommended by Kister and Trautmann, in which
the books are placed in a steam disinfecting oven, fitted with a
vacuum apparatus; formalin is placed in a vaporiser at a point in
the oven most distant from the vacuum apparatus, and as the pressure
inside the oven is reduced, formic aldehyde and steam are liberated
at about 80 deg. C.; this is continuously sucked through the
apparatus for thirty minutes, the books being disposed in the track
of the vapours.