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My own results are in perfect accord with those obtained by Russian, Aus- trian, and German Plague Commissioners, who concluded that plague could be conveyed to rats by feeding them on plague infected material, and that in a state of nature, rats generally become infected in this manner.

GENERAL SOURCES OF INFECTION.

(1.) Direct from man.-Urine, fœces, sputum, etc.

(2.) Direct from rats.---Contact, food, urine, fœces, saliva.

(3.) Food.

(4.) Contact with Infected Matter-In infected houses, in infected ships.

clothing, cargo merchandise. etc.

5. Other vermin.-Mice, cockroaches, ants, flies.

Many of the headings included in the general table on rat plague, are sufficiently clear in themselves.

Unfortunately, I find it impossible to deal with these thoroughly at the present time.

WILLIAM HUNTER.

The Relation of the Epidemic to the Epizootic.

The dictum of KoсH and many epidemiologists that plague is primarily a disease of the rat, secondarily a disease of man, and that epidemic plague is en- tirely dependent on the presence of widespread plague infection in rats, has become widely recognised and accepted by many plague experts. If we look into the evidence in favour of such a conclusion, little information of a definite nature can qe obtained.

Up to the present time, no research has been accomplished which would jus- tify the conclusion that plague rats are the only sources from which the virus is communicated to man. We must admit that there is a good deal of evidence in favour of such a method, but, notwithstanding the constant influx of additional supplementary proof, there yet remains to be proved, the direct connection between epizootic rat plague and epidemic plague.

Rats and man suffer from plague. They are susceptible to an identical affection. This is practically the sum total of what has so far been accomplished in regard to the part played by the rat in the causation of human plague, Asa- BURTON THOMPSON, in his Report on Plague in Sydney for 1902, gives an excel- lent resumé of the present status of our knowledge in regard to the rat question.

He has come to the conclusion that our promise of saiety for the future lies in habitually excluding rats from inhabited premises Although admitting the justification of the rat theory of plague, he sees, like I did myself, many obstacles in the path, before a clear understanding of the factors underlying the whole question is attained.

Notwithstanding the dogmatisms of some plague experts in regard to the part played by the rat in the production of plague epidemics, much still remains doubtful. The conjectures that rat plague is frequently communicated to man or, as ASHBURTON THOMPSON says, that man and the rat in the usual circumstances of propinquity are recriprocally infective, require considerable systematic research in order to establish definite proof.

In Sydney, every effort was made to settle the question. Much supplement- ary evidence was obtained. The conclusion was drawn that infected rats play an important, if not the most important, role in the dissemination of the disease.

Again, statements are forthcoming that epidemic plague may exist in the absence of an epizootic, that human plague may exist for some time previous to the appearance of the disease amongst rats, and that epizootic rat plague does not in every case precede or lead up to an epidemic among men.