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water should be slowly evaporated above the flame of the spirit lamp, and mounted in Canada Balsam which has been heated for a few seconds after being on the slide. Then examine with a 1/12th inch oil immersion. The bacilli are often few and far between, but it is of the utmost importance that a careful examination be made in cases where no glandular swelling can be felt and where the diagnosis is doubt- ful. During the latter part of the epidemic about 80% of the cases were diagnosed by the microscope alone, involving many hours' labour a day on what to most people is not interesting work. Once the bacillus is found the case is one of plague. Should the bacillus on the other hand be absent it does not necessarily follow that it is not plague. On one or two occasions we had to wait for the post mortem examination to give ns the cause of death. 1 put a hypodermic needle into the spleen (where the bacilli are generally abundant) in order to verify the diagnosis of one case. If a case is diagnosed plague then this examination completes the chain of evidence. In the case of a bubo which may or may not be a plague one it is advisable to take the blood direct from the gland, by a hypodermic needle or through a small incision with a tenotomy knife. These details are well known to bacteriologists, but unfortunately every one is not a bacteriologist.
For diagnostic purposes it is sometimes necessary to get a culture on agar- gelatine or blood serum. This has to be done in the most careful manner, as far as precautions are concerned, in order to get a satisfactory result, for it is to be remembered that in out-of-the-way places where plague may develop it is not always easy to obtain agar-gelatine or blood serum and even if obtained it is a tedious process to get them properly sterilised. Other points on the bacillus will be touched upon later; what has been written is enough for symptomatic or diagnostic purposes.
DIFFERENTIAL DIAGNOSIS.
When diagnosis has been reduced to a question of microscopic examination there cannot be much to be said upon the subject. The only difficulties we had in determining cases, previous to Dr. KITASATO's discovery, were with bad malarial fever cases, lymphangitis with irritative bubo of leg; one or two inflamed glands of the neck, and enteric fever. As regards intermission of temperature I cannot bear out CABIADIS' statement that no intermission occurs in plague. Intermissions do occur.
A case of mistaken diagnosis No. XII. is given which was diagnosed by us as not plague owing to the absence of head symptoms, and on account of other reasons which are given. Another case of mistaken diagnosis is given which, even before microscopic examination was made, we pronounced to be not plague, because of the absence of a symptomatic tongue, head symptoms, and the pulse usually met with in plague, and on account of the presence of another cause for the illness.
The question as to whether there has or has not been exposure to infection should weigh little or nothing at all during an epidemic of plague for there are many roundabout methods of infection.
One serious difficulty we had in determining the cause of death in dead bodies. required for burial purposes, more especially towards the end of the epidemic. The mortuaries situated in different parts of the Colony had to be examined regularly every day, but as the very idea of post mortem examination had to be kept in the background, the difficulty of being able to tell fairly accurately whether a person had died of plague at once becomes apparent. If the Chinese had been allowed to remove their bodies, as they wished to do, it might have been expected that plague would break out in outlying places. It is to be remembered that in Hongkong the Chinese are allowed to exhume the dead after an interval of seven years; there was therefore all the more reason for getting every plague corpse buried in a special cemetery where exhumation was not to be allowed. Swollen glands were the first thing to look for, then sordes in the mouth, then the special appearance of the tongue. Often the bodies bore the typical "facies" of the disease after death. The occurrence of the pink blush round mosquito bites, with any haemorrhages apparent, also helped to determine where the corpse should be interred. Micros- copic examination of blood removed from the spleen will probably be the method of diagnosis in these cases in future. Typhoid fever is a disease possible to be mistaken for plague-vide Case XVI.
PROGNOSIS.
There is no one special sign that gives hope for recovery, whilst there are many that are decidedly bad, and which are valued according to the ordinary ideas of medicine. Buboes do not suppurate as a rule until the primary fever has fallen, by which time you know that the patient is better.