20 REPORT OF THE IMPERIAL INSTITUTE OF VETERINARY RESEARCH,
as in the case of the buffalo blood. Specially selected large hill bulls were therefore pur-
chased in considerable numbers to be utilized as continuous producers of anti-hæmorrha-
gic septicæmia serum.
The research work on this disease envisaged in last year's report yielded fruitful re¬
sults later in the year. It was found that, (i) the " passage " through rabbits of the strain
of organism used for immunization did not bring about any exaltation in virulence for
bovines after it had been maintained in laboratory media for some time : (ii) exaltation
in virulence for bovines of a much degraded culture could only be brought about by
" passage" through bovines; (iii) cultures of much degraded virulence (" avirulent "
except when inoculated in very large dosages) were as effective antigens as highly exalted
cultures in the production of potent anti-serum ; (iv) there was no advantage in intra-
venous over subcutaneous injection of the cultures, as judged by the relative potency of
the sera obtained ; (v) if a sufficiently large quantity of antigen is administered as an ini-
tial step, simultaneously with a protective dose of anti-serum, the buffalo furnishes as
the result of this mere initial intervention in a few days a serum of high potency ; (vi) re-
peated injection of the culture dose at definite intervals does not result in an increase
of potency, but the serum potency can be retained in this manner at a satisfactory high
level for a long time,—many months (our tests have not been prolonged long enough yet
to enable us to assert that the serum is thus maintained indefinitely); and (vii) there
is no advantage gained by injecting very large doses over that obtained by injecting a
" sufficiently large " dose ; thus, no better serum is produced after the injection of 1000 c.c.
of good broth culture than is obtained after 100 c.c., though 10 c.c. is not sufficient to
produce the desired result. The principles that govern the production of immune serum
against hæmorrhagic septicæmia are therefore of the same order as those which we now
know to be necessary for obtaining good serum, economically, against rinderpest.
Briefly, as the outcome of these researches, the old system has been entirely abandoned
and the programme of manufacture of hæmorrhagic septicæmia serum adopted since the
commencement of 1925 is :—
(a) Cultures of " low " virulence are grown at Muktesar in bottles, each holding
200 c. c. of broth. The broth, known as " Bombay broth," is a cheap product,
made by the simple acid digestion of all the meat of carcases, and is of the same
kind as has been used for some time at the Bombay Bacteriological Laboratory,
Parel, in the production of anti-plague vaccine. It contains no added " pep-
tone," and is thus much cheaper than the ordinary broth employed in labora-
tories It is especially good for the growth of pasteurella organisms, and
for the glanders bacillus ; it has now been substituted with striking success
for the ordinary broth in the preparation of mallein (see later).
(b) The culture bottles, after their purity has been ascertained, are sealed and des-
patched to Izatnagar. The contents of one bottle are inoculated into a buffalo
subcutaneoualy, two days after the animal has been administered a protective
dose of anti serum (about 500 c. c., though with the low virulence of the
culture employed, the serum protection is not really essential). The buffaloes
used are those discontinued from anti-rinderprest serum production.
(c) Nine days after the culture injection the buffaloes are bled (at the rate of 8 c. c.
per lb. body weight) for serum.
(d) The producers are again inoculated with broth culture, at the rate of 100 c.c.
(for larger quantities tend to abscess production and are unnecessary) at once
after the first bleeding, and are b'ed again in nine days. This process of
culture injection and bleeding is repeated until sufficient serum has been pro-
duced to meet the anticipated demands of the ensuing season.
Serum produced in this way when tested upon hill bulls against the effects of 1 c.c.
of broth culture of exalted virus, 1/10 c.c. of which is a fatal dose, protects the majority
at 25 c.c. and all at 100 c.c.
A very solid immunity is produced by the injection of a small dose of live culture,
even of low virulence, simultaneously with a sufficient dose of anti-serum, but the revere
test of the laboratory has not been successful in demonstrating the efficacy of inoculation
with" dead " vaccines, although there is a wealth of evidence from the field that when
administered before the onset of the morbid season they are capable of setting up enough
immunity response in the inoculated animals to ward off the intrusion of the natural
disease. Following upon the heavy rains that occurred late during the last monsoon
period the vaccine was employed on a large scale by the Offg. Chief Superintendent, Civil
Veterinary Department, Punjab, to protect cattle in the flooded areas against denger