TUFAIL
AHMED
SIDDIQI
159
nature than that obtained by other methods of
inoculation.
Tuft [1931] studied the relative values of various
forms of inoculation, with particular reference to
the intracutaneous route in immunization against
typhoid, and found that the rate of antibody pro-
duction by the intracutaneous route was equal to
that by the subcutaneous route and slightly better
than by the intramuscular route, although the
total dose of antigen inoculated by the former was
one-seventh of the amount introduced by the last
two methods. It was also contended that since
the skin is richly supplied with reticulo-endothelial
cells it may well be adapted for the liberation of
the anti-bodies by the stimulus caused at the site
of the intracutaneous inoculation.
The experiments of Neufeld and Meyer [cited
by Tuft 1931], and a number of other workers
have revealed that the reticulo-endothelial system
plays an important part in the process of immunity.
Tuft [1931] also refers to the possibility of utilizing
the skin in a specific manner for the introduction
of antigens by other modified forms of inoculation.
These consist of inunctions described as 'per-
cutaneous method' by Petrushky et al. through
scarification
and
subsequent
inunction
described as 'cutaneous-method' by Pondrof,
the 'intracutaneous or sub-epidermal method'
of Wolff Eisner and Sahli, and the 'cuti-vaccina-
tion' of Besredka, [all references cited by Tuft
(1931)].
These reports suggested the possibility of uti-
lizing the skin for immunization against other
infections.
MATERIAL AND EXPERIMENTAL METHODS
The existing subcutaneous method of immuniz-
ing against rinderpest was compared with the scari-
fication method in an experimental group of ani-
mals. The latter method consisted in bringing
about an interaction between the host and the
virus through multiple foci of irritation within
a small area on the skin of the ear, and was a
modification of the intracutaneous mode of inocu-
lation, in that it enabled a relatively larger sur-
face and the entire thickness of the skin to parti-
cipate in the process of immunization. In this
method, the implantation of the virus and scari-
fication of the skin were accomplished simulta-
neously and thus required no-subsequent inunction.
The ear for this purpose offered certain advantages
over other parts of the body. It was easier to
manipulate, and the site where the antigen had to
be implanted, possessed a degree of natural pro-
tection against external influences. Being devoid
of flesh and provided with thin tender skin, the
ear was a favourable site for the points of the scari-
fier to penetrate to their full depth into the tissues
involved.
Scarifier (Plate XIII, fig. 1). The proper length of
the points of the scarifier was important. Ob-
servations on some dead cattle revealed that the
skin thickness on the inner side of the ear varied
from 0.8 to 2 mm. Hence, in determining their
length due allowance had to be made for such
variations, not only in respect of animals of the
same breed, but also in those of other breeds, to
ensure that the points of the scarifier could pierce
the entire thickness of the skin in all breeds, with-
out being long enough to penetrate beyond the
layers of the skin.
Vaccine. Goats that had shown a positive
reaction were destroyed on the fifth day after
inoculation. The spleen was removed and freed
from fat and fascia. The organ was then either
squeezed in an iron press or ground in a mortar,
distilled water being added to the pulp at the rate
of 1 c.c. to each gramme, and then transferred to
1 c.c. collapsible tubes—each tube containing
about 50 doses. The latter were then wrapped in
small pieces of paraffined cloth for storage.
Technique of inoculation (Plate XIII, figs. 2 and
3). A drop of vaccine from the tube was allowed
to flow and settle uniformly on the blade of the
scarifier. A small area devoid of hair and super-
ficial veins on the inner surface of the ear was
selected, preferably on the upper border of the
lower third region, and the part cleansed without
applying any antiseptics. This part was exposed
to view and a flat piece of wood held underneath
to give resistance. The scarifier was then pressed
firmly with a revolving action until contact bet-
ween the points of the scarifier and the cartilage of
the ear could be felt. In most cases this was
found quite adequate for depositing the virus on
the scarified site, but where it was not satisfactorily
lodged it was spread over from the surrounding
area with the flat end of the instrument. As
soon as pressure on the scarifier was relaxed, drop-
lets of serous exudate could be seen oozing out
(Plate XIII, fig. 4) from the lesions and mixing freely
with the implanted vaccine. The mixture gradu-
ally spread over the whole scarified area and ulti-
mately dried in crusts.
For practical purposes the above process was an
indication of a positive 'take', though not with
the degree of certainty as in other routes of in-
oculation. Judging from the brief period during
which mixing of the vaccine and skin-exudate
occurred, any artificial protection to the area was
considered unnecessary.
Animals. Altogether 29 animals, consisting
of 25 dairy calves and four hill bulls, were used
in the experiment. The calves were 7 to 17 months of
age and were born of Hariana animals, immunized
to rinderpest and belonging to the Institute herd