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The recent report, on the 4th outbreak of Plague in Sydney, by Dr. ASHBURTON THOMP SON, is of great interest in this respect. Since this observer commenced his studies of plagne epidemiology, he has been deeply impressed by the rat theory of the disease, the last report on Plague in Sydney [1904] is of importance in that, the views put forward are in perfect accord with my own. The conclusions adduced by THOMPSON are, that plague is dependent on plague rats, that there is a close relationship between the epimuic and the epidemic, and that an extermination of the rat means a staying of plague. In a city like Sydney, with a population composed mainly of whites, these results are of great value, confirming the observations made in Hongkong, under adverse circumstances, owing to the dense Chinese population and general insanitary condition of the City.

Further, my results have received confirmation in the hands of Dr. PAKES, who, in a recent exhaustive report on Plague in Witwatersrand in 1904 has demonstrated clearly the close connection between the outbreak of rat plague, and the occurrence of the epidemic. Human plague in Peru has also been traced to the occurrence of widespread epimuic plague. In a report in the Bull. de l'Inst. Pasteur. No. 21, on the prevalence of plague in Callao, special attention is directed to the role played by the rat in plague dissemination, and it is insisted that plague is not to be regarded as a very contagious or infectious disease. I have already dwelt upon this question in my special report on Plague, and drawn attention to the fact that. apart from cases of primary pneumonic plague, cases of plague may be treated successfully in the wards of a general hospital. Indeed plague patients have been treated successfully in well ventilated rooms of their own residences, without any extension of the disease to the other inmates of the house. The reports of the various Commissions, and in particular the Indian Plague Commission, express themselves strongly upon this point. It has even been said, that the wards of a plague hospital are the safest places during a severe epidemic.

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During the past year Professor MARTIN, Director of the Lister Ir cute, London, a Member of the recent Commission, sent to India to investigate Plague, c

nunicated with

me re the Rat Theory of Plague Epidemics. I furnished him with all the details at my disposal, and from what I have heard, that Commission is devoting a considerable part of its time to the question of the rat in spreading plague, and the importance of this rodent in plague epidemiology. Their results will be awaited with considerable interest.

So far as one can gather, this theory of plague epidemics would appear to be steadily gaining ground, and it is to be hoped that with the establishment of such a theory on a firm basis, and the knowledge of the methods of communication of the infection from rats to man, our sanitary and prophylactic measures against the disease will be simplified and reduced to sound scientific principles, in a manner similar to the present-day methods of dealing with a disease like Malaria.

The results of the investigations in Witwatersrand show clearly that rats are susceptible to plague through the ingestion of infected food. That such obtains in Hongkong has been shown by me in my Report on Plague for 1904. In this Report, I noted the discovery of the B. pestis in rice, and the communication of the disease to rats by such infected food.

It is difficult to get away from the possibility that food has something to do with the spread of the disease. Ingestion is a common mode of conveyance of the infection in rats, and other animals. It remains to be proved, if such a method of infection obtains in man. Plague infected rats, through their secretions and excretions, may disseminate the B. pestis broadcast amongst articles of food used by the native. Indeed, paragraph 29 of ASHBURTON THOMPSON's recent Report is significant in that there existed a possibility of the infection of workmen's food by plague infected rars in plague infected places. These points, and other recently added facts in regard to the mode of infection in plague, show us, how hypothetical yet is the view that plague prevalence in epidemic form is built up of cases of direct cutaneous inoculation. In the light of many recent researches, the skin inoculation theory of plague would appear to lose much of its significance.

Domestic pets, e.g., cats, may also occasionally be of importance from the point of view of spreading plague. These animals are known to suffer from the disease, and it is most probable that they contract plague, through the ingestion of plague rats. Minor epizootics of cat plague have occurred from time to time in several endemic plague centres, including Hongkong. Recently its occurrence has also been noted in South Africa. My contention that ectozoa have little significance in the spread of plague is gradually receiving general confirmation. We possess no data at present to support the view, that micro-organisms of the bacillary form, e.g., the B. pestis, pass through a definite cycle of development in the body of an insect and that such an intermediate host is essential for the transference of the