RINDERPEST : TRANSMISSION BY CONTACT.              386

under experimental conditions; and if so, to obtain a preliminary idea of the
number of days of contact necessary.

It started on the 10th August 1929, and the proportion of affected to healthy
animals was adjusted to be an equal number of each. Thus on this date six hill
bulls were injected with rinderpest virus and turned loose in an enclosure within
one of the sheds used ordinarily for such experimental work at Muktesar, and on
the same day another six healthy, uninoculated hill bulls (called Lot A) were
turned loose with them in the same enclosure, and daily observations were made
upon them all. The enclosure consisted simply of a portion of the shed with the
partitions removed to form a " loose box ", in which the cattle were confined only
by posts and rails. They were left untied, and were fed and watered from common
troughs. After three days of this close contact, two of Lot A (Lot A-1) bulls
were removed, and observations were continued upon them thereafter in strict
isolation elsewhere. On the same day, namely, the third day of the experiment,
two new healthy hill bulls, Lot B, were turned into the enclosure to replace the two
which had been removed. Three days later again a similar change was made,
when two more of Lot A (Lot A-2) bulls were removed to isolation, and two new
bulls, Lot C, replaced them. Contact between the artificially infected and the
healthy bulls was maintained for a total period of sixteen days. As soon as one
of the infected animals died, one of the healthy cattle was removed to isolation in
order that an equal number of each should be maintained during the whole
experiment.

The artificially infected animals used in the experiment all reacted to the virus
injection given on the 10th August 1929, although two of them somewhat mildly,
ending in recovery. The other four bulls all showed severe and typical reactions
and died of rinderpest, one after seven days and the other three after eleven days.

Table I summarises the results obtained in the healthy animals that were in-
contact during the experiment, and they proved that it was possible to transmit
rinderpest by the method of close contact alone that had been used. Thus, hill
bull No. 595 of Lot A-2 died of the disease resulting from infection gained while in
contact; and both hill bulls No. 488 of Lot A-3, and No. 475 of Lot B reacted
typically, and, although they recovered from the attack, they were both solidly
immune to a subsequent immunity test when virulent blood was injected.

The results also showed clearly, however, that even with an equal number of
affected and healthy cattle kept in the closest possible contact, rinderpest definitely
failed to develop in as many as half the number of animals used in the experiment.
Failure in this respect was certainly to be expected in the case of the pair Lot A-1,
since they were in contact only for three days of the incubation period in the ex-