142    INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, II

     Of the animals which completed the experiment, 53 showed no definitely
appreciable reaction, either at the time of inoculation or after the test dose, and
it is presumed that at the time of the initial inoculation the virus in most, if not
all, of these animals was capable of multiplication and diffusion to a sufficient
extent to stimulate a durable immunity, although the effect was not sufficient to
produce symptoms appreciable to the ordinary methods of clinical examination.
Support is lent to this view by the fact that the great majority of the animals in
this group were immunised between the ages of 4—8 months, at which period we
have generally found that calves are definitely susceptible to rinderpest, although,
as it is the custom to wean calves about 4—6 months old, the susceptibility at this
age is not as great as at later periods.

     Unfortunately no subinoculations of blood were carried out from any of the
calves at the time of serum-simultaneous inoculation so that definite evidence of
the presence of the virus in the blood at this time is lacking.

     Thirty one calves, consisting of 10 indigenous, of which 7 were of Sahiwal
breed, and 21 European crosses, gave a more or less definite reaction at the time of
immunisation and these animals, with three or four exceptions, gave no reaction to
the subsequent test dose.

     In the exceptions noted, the reactions to the test dose were very indefinite,
and in the absence of control subinoculations, it is not possible to state that either
the original reaction or the " test " reaction was due to rinderpest. In any case,
if such double reactions do occur, they would appear to be very rare.

     A point of considerable interest in this group is that although the majority
of the calves (approximately two-thirds) were six months of age or over, the
remainder under six months gave evidence of a definite reaction, which was very
much more marked in the case of the animals lent by the military dairies than in
the case of the locally bred calves, and we presume that this difference is due to a
possible difference in the immunity of the parents.

     Finally there is a group of 14 calves which reacted in varying degree to the test
dose, indicating that the diffusion or stimulation of immune response on the part
of the original virus was incomplete or in some cases entirely absent. The distri-
bution of these calves according to breed, age and interval of test is given in
Tables II and III.