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not to the degree insisted upon by some. The significance to be laid upon the presence of bipolar and oval shaped bacteria is dependent upon the evidence- which one has to suspect plague. In man the presence of such micro-organisms in a bubonic swelling, in the blood or the sputum, during an epidemic of plague would justify one in concluding that the organisms were B. pestis. In the absence of plague, however, the mere finding of such bipolar bacteria does not justify such a diagnosis. The morphological appearances may be very suggestive but in isolated instances like this one requires further confirmation in the shape of cultural and inoculation tests.

Again in man, even during a severe plague epidemic, the microscopic examin- ation of blood smears has to be undertaken with considerable care. In the absence of a bubo, symptoms may be present indicative of some infection, and a hastily or carelessly taken blood film may show beautiful bipolar bacteria, which are microscopically almost identical with the true B. petis, yet the further course of the disease and the negative results obtained with carefully taken biood smears clearly prove the case to be something entirely different.

After the results obtained in Hongkong by Dr. BELL, and others, all of which I have confirmed, one would require to exercise considerable caution in diagnosing the B. pestis in any blood smear, unless the latter be prepared very carefully. As Dr. BELL noted in a report to the Government in 1903, beautiful bipolar shaped bacteria can be demonstrated in the saliva, fæces and in various other parts of the body. I have made similar preparations and have convinced myself that it would be well nigh impossible in many instances to microscopically distinguish such micro-organisms from the plague bacillus. In the past too great weight appears to have been laid upon the mere microscopic examination of a sinear coloured with some simple aniline dye like methylene blue. In fact this simple- method is regarded by many as sufficient. As pointed out by the various Indian Plague Commission, however, such a rough and ready method, applicable and diagnostic enough in many instances, may lead one to very erroneous conclusions. An important point is noted by the English Plague Commission, namely, hel diagnosis of the presence of plague bacilli without the use of other tinctortia methods of examination such as the reaction to GRAM's method of staining. In doubtful cases, and more particularly in the absence of an epidemic of plague, such an important tinctorial test should never be neglected. As micro-organisms are known which microscopically resemble the B. pestis, but give a positive result with aniline water gentian violet after treatment with iodine solution.

When one has to deal with the diagnosis of plague in animals, the question of microscopical examination as a sufficiently diagnostic test, becomes one of great difficulty. In Hongkong, where thousands of dead animals are examined for the presence of plague bacteria, the only possible inethod of examination is the micros- copical, and the results obtained by such a method must not be regarded as strictly accurate but only approximately so. It is none a widely recognised fact that disease in the lover animals is frequently excited by micro-organisms morphologically almost identical with the B. pestis. In particular one may mention the group of hæmorrhagic and septicemic diseases which appear to be exceedingly prevalent throughout China, especially the diseases known as cattle plague, fowl cholera and in all probability a variety of swine plague. These diseases are called forth by bacteria which show bipolar staining even more markedly than the B. pestis, and the only differential point between them and the latter, is put down by some as a question of dimeusion. These hæmorrhagic septicemic micro-organisms are said to be smaller in size than the B. pestis. As I have already mentioned such a distinctive point is one upon which little reliance must be placed owing to the variations met with amongst bacteria when placed in different surroundings.

Again bipolar staining has been met with in the B. typhi by GOTSCHLICH and micro-organisms are found in rats which have a great resemblance to the B. pestis. Therefore, viewing all the evidence before one, it is clear that the system- atic examination of a large series of dead animals for the B. pestis by the micro- scopic method is liable to lead us to fallacions results. This circumstance has been constantly before my mind since I commenced such an investigation at the Govern-- ment Public Mortuary, and I have always insisted that the results of my examina- tions must be regarded as approximate only. It would be quite impossible to do otherwise. The determination of the presence of plague bacilli in strictly scientific