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The longest time on record for the persistence of the B. pestis in a dead body is 30 days (YOKOTE, Cent. f. Bakt., 1898).

It is extremely probable, however, that in most cases, the bacilli are dead long before this time. The observations have usually been on the dead bodies of small animals, e.g., Guinea pigs. In the human body, the chances are that the plague bacillus would survive for a much shorter period of time.

Further, a good deal depends upon the general nourishment of the body. Plague corpses do not usually present much abnormal in this respect. Climatic influences also affect the life of the B. pestis. In a semi-tropical climate, like that of Hongkong, where decomposition is usually so rapid, plague bacilli must quickly disappear, or be rendered inert within a few days after the death of the individual.

Again, plague bacilli have never been found in the earth surrounding coffins containing plague corpses. This is important when we remember that the length of life the B. pestis in ordinary earth may be considerable. GLADIN (Cent. f. Bakt., 1898) found the organisin alive after one to two months.

WILLIAM HUNTER.

The Spread of Plague Infection by Insects.

The spread of bacterial infection in general by insects has been the subject of widespread discussion within the past few years. This is due mainly to the possibility which has arisen in regard to the mode of infection in plague and the possible spread of the disease by such means.

The spread of infection by insects is by no means a new subject. It has been discussed for ages. So far as plague is concerned, history supplies us with very early records of its supposed spread by way of insects.

In the year 1498 Bishop KNUD of Aarhus noted that the first sign of the approach of plague is a change in the weather with excessive fog and rain and the appearance of large numbers of flies."

This observation seems to have been forgotten because, until quite recently the role played by insects in the spread of plague or even other infectious diseases, was passed over as unimportant and undeserving of scientific investigation.

During recent years, however, quite a revival of the old doctrine has taken place, and numerous contributions have been made to scientific literature in regard to this subject.

The literature is so voluminous, fragmentary and scattered. that it has only been after careful and prolonged searching, that anything like a comprehensive review of the present state of our knowledge, bas been possible.

It has seemed probable to many investigators that insects do play an impor- tant part in the spread of infection. In certain diseases, there is no doubt of the fact. One has only to live in a country which is malarious to satisfy one's self as to the role played by these pestiferous inosquitoes, namely, the species of anopheles.

The East may be regarded as the breeding ground in chief of all sorts of insect life and such is rampant in China. Opportunities are afforded in the far East for the study of such species, and in a place like Hongkong, no better chances could be offered to establish or disestablish the doctrine of the insect sprend of plague. Leaving the subject of plague for the present, it seems necessary, in order to grasp the subject under consideration, to consider certain points. Summing up the means at the disposal of insects for the transmission of an infectious virus, we arrive at the following:-

I. The factors necessary for the infection of the insect.

(a.) The deposition of germs on the surface of the insect. (b.) The introduction of viri into the intestine of insects. (c.) The virulence of the virus infecting the insect.