Sessional_Paper_1905 — Page 449

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Except under the action of a strong wind, which is not found inside houses, it is extremely improbable that infective excretions, secretions and discharges from plague patients can be disseminated in the atmosphere until such matters are dried and pulverised. Further there is the action of saprophytic organisms to be considered. When any organic matter is discharged from the body it rapidly be- comes a culture ground for saprophytic organisms. It is highly probable that such organisms being adapted for growth outside the animal body would speedily crowd out the plague organisms which have just been expelled from their host and are therefore under conditions not suitable for their preservation.

The Indian Plague Commission reports (page 102) that the plague bacillus has never been detected in the floors of native houses (in India) by any trust- worthy observer. Although this means no more than that present methods have failed to detect it, yet it is very strong evidence that the plague organism is soon crowded out and killed by saprophytic organisms,

An exception with regard to the presence of bacillus pestis in the air must be made in one respect.

The Government Bacteriologist says (op. cit., page 39) that primary pneu- monic plague is caused by the drop infection of FLÜGGE.

It is perfectly reasonable to suppose that a person suffering from pneumonic plague may in the act of coughing or of any forced expiration discharge droplets of infective matter into the air in his immediate neighbourhood. This would constitute a grave danger to other persons in reach of such droplets and hence in this connection overcrowding is again a factor.

However with this exception I cannot hold that the respiratory tract is the channel by which the virus of plague usually gains entrance to the system.

On reviewing these three channels of infection, namely, the skin system, the alimentary tract and the respiratory system, I must conclude that, with the ex- ception of primary pneumonic plague, the usual mode of entrance of the virus is through the skin.

This is the view which obtains generally, and particularly in India, and is the result in that country of painstaking work and observations over a considerable number of years.

Rats and Plague.

That rats are susceptible to plague has been proved. As these animals live frequently in close association with men there must, therefore, always be a danger of plague occurring in human beings if infected rats are found in the locality. Such a measure, therefore, as disinfection is as necessary in a house where a plague infected rat has been found as where a human case has occurred. Therefore it is necessary to adopt measures to keep rats out of buildings by rendering the insides of the houses rat-proof.

Since the visit of Professor SIMPSON to this Colony these measures have as far as possible been systematically carried out.

All rats collected by the staff of rat-catchers are daily sent to the Public Mortuary and are there examined. A return is made to the Sanitary Department on the following day shewing what rats, if any, are deemed to have been infected with plague.

Should any such rats have come from any known premises; disinfection of them is then carried out, rat runs and holes are noted and are filled with cement under notice from the Sanitary Board,

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This method of discovering infected rats is not, however, exact. We do not get a return of rats known for certain to be infected but merely of those suspected of being infected.

There are other micro-organisms than the bacillus pestis which are morphologi- cally indistinguishable on mere microscopic examination from the plague bacillus.