5

The following tabulated statement shows the numbers of calves purchased
or hired, the numbers of doses manufactured, the average numbers of doses
yielded per calf, the total gross cost and the total revenue and the average
net cost per dose for four years :—

The working cost of the Department for the year amounted to Rs. 22,183-
0-11 against Rs. 34,936-14-6 in previous year.

There was thus a large saving in spite of the greatly increased cost of
glycerine, lanoline, kerosine, and packing materials owing to the war.

An epidemic of foot-and-mouth disease again stopped the work of the
depôt temporarily last year, but the output of vaccine has been ample. The
chief loss from such epidemics arises from the loss of calves and of vaccine
in the making, as the sick calves have to be discarded.

This loss, together with the loss of calves from accidents and other causes
greatly diminishes the apparent output per calf, which has really been
greatly increased by improved feeding and technique, and is actually about
5,000 doses per calf kept and used.

The system of direct fortnightly issues to vaccinators has been continued.
The cost to the Depôt is greater, as the number of postal packages is larger ;
but the results are good. There is no loss of time or of the freshness of the
vaccine, and there is really an ultimate saving owing to the packages being
posted only once, instead of issuing to Civil Surgeons, and being reposted
by them.

12. Experimental work.—Further experimental work was carried out at
the Depôt during the year with some very interesting  results. Last year it
was demonstrated that glycerine vaccine was the most stable preparation for
withstanding the vicissitudes of high temperature and travelling. This year
we have compared the stability of vaccines which were respectively slightly
acid, slightly alkaline and neutral and also of vaccines which were prepared
with distilled water, boiled water and normal saline solution, and we have
found that neutral vaccine is the most stable and that distilled water is
a much better diluent than either boiled water or normal saline solution.

Another series of experiments has demonstrated that glycerine vaccine,
which is neutral in reaction to begin with, becomes acid slowly in cold
store and rapidly becomes acid when exposed to room temperature. As
we have already proved that acid vaccines are not stable, the result of this
experiment supplies us with the explanation why vaccine deteriorates
rapidly after issue, and becomes inert in from ten to twenty days according
to temperature. It is really a question of acidity which is presumably
produced by the living virus in the vaccine.

Another experiment showed that the bacterial content of the vaccine
as shewn by plate cultures diminished much more rapidly when the vaccine
was kept at room temperature than when it was kept in cold storage. This
is also presumably due to the more rapid production of acid at the higher
temperature which, while it reduces the number of extraneous organism