PRESIDENCY VACCINE DEPARTMENT.                 9

of the question has been found, every medical officer will be able to
assist in the enquiry by experimenting with likely agents. It is only
now a question requiring time and observation, to determine the
relative capabilities of different substances in definite proportion, in
accomplishing this end.

Though it has been indicated that salting the lymph in a good
method, it cannot yet be predicated what will be found the best pro-
cedure.

In the course of these experiments it has been determined that
cobra poison (another animal virus) loses its potentiality by keeping.
Two specimens of dry cobra poison, which had been long kept in a dry
state, were found to be inert. Solutions of these specimens were injected
below the skin of pigeons, without effect.

The influence of temperature in facilitating decomposition was early
noticed during these enquiries. In the early months of 1865, stores of
lymph were shut up in the expence magazine of the Calcutta Ice-house.
The temperature was not sufficiently low to resist the extreme tendency
to decompose, and the experiment was a failure.

As even a few extra degrees of heat favour the production of such
changes (whether antiseptic agents are used or not) it has been found a
useful precaution to expose the tubes to the air as little as possible.
They are habitually kept in porous vessels filled with water. The
evaporation, when the air is dry, tends to reduce the temperature of the
water, and though a very simple measure, the precaution is sometimes
very efficacious in delaying the changes which it is wished to guard
against. I consider that this practise is so useful, that it deserves to be
made generally known to others, who may have experienced the same
difficulties in preserving a little store of lymph even for short periods.

Other modes of
retaining virus
active.

12. As my experience of the fluid lymph stored in tubes, differed so
much in India from my former experience of it, (at a time when it seemed
uncertain, as to whether success would be arrived at, in the endeavours to
keep lymph in a fluid state) some experiments were made to ascertain
the feasibility of keeping crusts or dried virus in an active condition.
Since so great a necessity for the investigation has not existed, such an
enquiry has been partially desisted from; it doubtless deserves, however,
future prosecution. As one instance, further exemplifying the direction
experiment ought to take, it may be stated that the virus was rapidly
dried over strong sulphuric acid in the exhausted receiver of an air

b