Sessional_Paper_1901 — Page 653

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Experiment No. 2.

On the 17th July, two bealthy rats A and B were fed with the virus-ten tubes being used in half a pint of salt

water :-

A died on the 21st July,-four days after being fed on the virus-and three healthy rats which had been put in the same cage would not touch the body.

B died on July 27th,—ten days after being fed on the virus-and its body was partly eaten by three healthy rats C, D, and E.

C and D died on the 31st July,--four days after eating of the body of B. The body of C was partly eaten by three healthy rats, F, G, and H; the body of D was not eaten.

F and G died on August 2nd,—two days after they had eaten the body of C—and the dead body of F was partly eaten by two healthy rats, I and J, while the body of Ġ was similarly eaten by two healthy rats K and Ž.

I died on August 6th,—four days after eating the body of F—and a healthy rat in the same cage with it would not touch the body.

E died on August 8th,-twelve days after eating of the body of B—and its body was partly enten by a healthy rat M, which had been placed in the same cage.

H died on August 11th,-eleven days after eating of the body of C—and a healthy rat in the same cage did not touch the dead body.

I died on August 13th,—-eleven days after eating of the body of F—and two healthy rats in the same cage did not touch the dead body.

K died on August 14th,-twelve days after eating of the body of G-and two healthy rats in the same cage did not touch the dead body.

Z died on August 15th,~thirteen days after eating of the body of G-and its dead body was partly eaten by two healthy rats A and O.

M died on August 21st,-thirteen days after eating of the body of E—and two healthy rats in the same cage did not touch the dead body.

As a counter experiment several rats have been kept in the same place and under precisely similar conditions, with a view to ascertaining whether they would survive in captivity, if not infected with the virus, and these have remained in good health with the exception of one, that died as the result of an accident. Thus on June 25th, twelve rats were procured; ten of these were used in connection with experiment No. I and six of the ten have died, presumably as the result of the infection. Of the remaining two, one died as the result of an accident incurred while transferring the animal from one cage to another, and the other is still alive.

Between June 29th and July 1st, uiueteen ruts were proenred, of which fifteen were used in connection with experi- ment No. II; thirteen of these have died after infection, while the four which were not used for the experiment are still alive.

It will thus be seen that the the period which may elapse between the date of infection and death varies from two days to twelve or thirteen days, and that not infrequently healthy rats will not touch the dead bodies of the infected ones,

The proposal is to feed healthy rats on the virus and then to let them loose again, in the hope that they will die of the infection and that then other rats will feed on their dead bodies and will thus become themselves infecte:l.

The objections to the proposal are that the rats may die in private dwellings and thus create a nuisance, and in any case no check can be kept upon the experiment after once the rats are set free.

I am not therefore inclined to recommend the adoption of the proposal by the Government on any extensive scale but if any owners of gedown property desire to experiment in the matter, I have now a sufficient number of inferted rats to be able to supply them with a few for the purpose.

It is very doubtful if rats can infect human beings in any way, so long as they are kept out of the dwelling-houses, and I think that the efforts both of the Sanitary Board and of the householders would be best directed to securing this cnd by keeping all drains and drain-fittings in perfect order, maintaining an impervious covering to all earth surfaces within the dwellings, by the removal (as far as may be possible; of all ceilings, wooden skirting-boards and lath-and-plaster partitions, and by avoiding the accumulation of garbage within or in the neighbourhood of the dwellings,

I have the honour to be,

Sir,

Your obedient Servant,

FRANCIS W. CLARK,

Medical Officer of Health.