38
REPORT OF THE IMPERIAL BACTERIOLOGICAL LABORATORY,
the " aerial envelope or cushion " tending to develop around the animals
was susceptible to rapid displacement.
It has been stated in the section dealing with the routine manufacture
of anti-rinderpest serum that an experimental plant had been obtained
for the tests upon the desiccation of serum in vacuo at low temperatures.
The results have not been very encouraging on account of the fact that
in this type of plant the serum had to be placed in pans, in which ex-
cessive frothing took place and ultimate drying was very difficult. Per-
haps, tests in which the principle of spraying the liquid on to a revolv-
ing drum is adopted may be more successful.
Mr. J. Da Costa was responsible mainly for the execution of the ex-
perimental tests on the immunity of rinderpest.
(c) Hæmorrhagic Septicæmia. Researches upon this disease were
directed with the object of ascertaining more information upon the pro-
perties of the virus and evolving better methods of securing products
for combating the disease. In the past, considerable difficulty had been
experienced in arriving at an estimate with regard to the efficacy of the
products used for this purpose. The value of the anti-serum can now
be very accurately determined by using the natural hosts for test purposes
(hill-bulls discontinued from rinderpest have been used). It would
appear certain that in the dosage recommended by the laboratory for
use in the field the serum is capable of warding off a virulent fatal in-
fection, for administered in substantial amount experimentally it obli-
terates the effects of a dose of culture virus, obtained after exaltation
by passage through the natural host, that would certainly kill a " con-
trol " animal. Having, therefore, established a method for testing the
potency of an anti-serum steps were taken to develop optimum means
of serum production. The serum produced after intravenous hyperim¬
munization with culture was of almost the same value as that produced
after repeated subcutaneous injection, but whereas the former method
tended to produce considerable mortality after the development of
arthritis, the latter method tended to cause excessive local disturbances
at the seat of injection. In earlier work, growth obtained on solid
media seemed to be best and most economical for injection, but sub-
sequently it would seem that for routine purposes a liquid medium made
on the principle of Martin's broth was preferable for routine cultivation
(" peptone " obtained by auto-digestion of pigs' stomachs and liver
according to the method of Meyer and Stickel, buffered with phosphate,
added to muscle or heart extract, heated 80°C, passed through bacterial
filter for sterilisation). " Slow " methods of preparing serum producers,
by repeated inoculation with " dead " culture, and then with gradually
increasing doses of culture of low virulence proved very disappointing
when carried out at Izatnagar during the cold season 1923-24, for the
mortality during the various stages was excessive. Curiously, a serum
of high potency could be obtained after immunization of the buffalo
serum producers with cultures of greatly degraded virulence. Mortality