CORRESPONDENCE.
121
with rinderpest but the recent lesions of rinderpest are so familiar to workers in
this Institute that it would be difficult to imagine such lesions being overlooked or
wrongly read. Admittedly, there is much to learn regarding the lesions of old stand-
ing cases and one would not be justified from a knowledge of acute lesions only in
jumping to conclusions as to whether or not lesions such as we encountered could
occur in chronic and very old standing cases. Again deep and necrotic ulcers occu-
pying an area larger than a rupee in the caecum and rectum are not met with every
day and in the ordinary experience of rinderpest workers. Delpi has reported
mouth lesions in cases 1½ months old, and recently Gibbs [1933] has described the
presence of diphtheretic lesions in cases of some months' standing. The lesions
in the anterior portion of the alimentary tract in our bull cannot, therefore, b e
taken as proof positive of a recent infection. It rather shows that careful observa-
tions may reveal similar lesions in animals lingering after apparent recovery from
rinderpest.
Mr. Purvis thinks that the conditions existing in tin shed were very favourable
for a later infection. Hill bull 288 was housed with others, discontinued at least
16 days after the administration of the virus, as is our routine practice. Evidently
he had not noticed, from Cooper's article in the same number of the Journal, how
almost impossible it is to set up infection by contact from animals recovering from
rinderpest. In suggesting such a possibility as this, he virtually concedes our
thesis that recovered animals may harbour the infection.
Among those who have, since our attempt, examined the possibilities of carriers
in virus diseases, Gibbs [1933] found that 4 out of 7 cattle recovered from rinderpest
harboured the virus for periods varying from 32 to 177 days after natural infection.
It is unfortunate that complete details of his observations have not been published,
and the employment of calves 6 weeks old for experimental tests is a decided draw-
back. Further from the analogy of a carrier state in the salivary virus of guinea
pigs and the mosaic disease of plants, Doyle [1933] thinks that " with the elabora-
tion of more refined technique, it may yet be shown that animals recovered from
certain diseases retain minute quantities of virus over long periods in the system ".
For purposes of analogy with other virus conditions we may refer firstly, to human
poliomyelitis, in which occasional convalescent carriers lasting for seven months
have been proved ; secondly, to equine infectious anæmia in which " the relaps-
ing carriers continue to harbour the virus and through its elimination in the urine
are a menace to the health of other animals " ; and thirdly, to equine influenza
where stallions recovered from the disease may harbour the virus and infect healthy
mares through coitus several months or even one or two years after recovery. In
the last named condition, Poels (cited by Hutyra and Marek) was able to infect
healthy horses through intravenous injections of filtered semen from a stallion which
for a number of months had infected mares bred to it, and Basset (Comp. rend.
des. seances de l'Academie des Sciences, 1911, CLIII, 485) demonstrated that the
blood of a horse which had recovered from an artificial inoculation was infectious
for three and one and half months subsequently.