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manner in each individual animal would necessitate numbers of assistants and besides entail considerable expense which I think is quite unnecessary. During the past year birds of various species were examined bacteriologically and a few returned as plague infected. As I mentioned in my Annual Report for 1903, it is quite possible that some of these were in reality cases of fowl cholera, but in the absence of cultural and experimental tests, it was impossible to determine the exact nature of the disease in each case.
Similar remarks apply to the presence of plague-like bacilli in rats. Several micro-organisms have been described as occasioning septicemic disease in these animals, and their morphological appearances are by no means unlike the B. pestis. But as already stated, it is impossible to determine the exact nature of the bacilli in each animal and that the results aimed at are merely approximate.
The difficulties of approaching the diagnosis of the presence of plague bacilli in animals is greatly enhanced by the experiments of SIMPSON and myself showing the possibility of the occurrence of plague infection in almost every animal met with in Hongkong.
The B. pestis bas never been found to retain the stain by GRAM's method. KITASUTO'S observation in this respect would appear to be wrong.
PITFIELD'S method of staining gives excellent pictures of the mucous cap-ule of the B. pestis. Good specimens of this covering have been obtained from rats.
The B. pestis has never been found to possess the power of motion. The biological characteristics of the B. pestis met with in Hongkong are practically identical with those found in other parts of the world. HANKIN'S method of diagnosis of the plague bacillus has been found of great value.
The B. pestis grows exceedingly well in media prepared with rice. This would seem important in regard to the diet of the native Chinese population.
WILLIAM HUNTER.
The Length of Life of the Bacillus Pestis.
The plague bacillus is a non-sporing micro-organism. So far as we know, its existence as a saprophyte must be very limited.
The experience of those who preserve living cultures of the B. pestis for any length of time, would show that, under certain circumstances, this limited extra- corporeal existence is subject to variation. Pure cultures of the B. pestis, pro- tected from the deleterious action of drying, and light, and kept in a cool place, may remain alive for months or even years.
SCHULTZE (Cent. of Bakt. Bd. 29) kept the bacillus alive for 4 years on MAR- MOREK'S bouillon. GOTSCHLICH (Zeit, of Hyg. Bd. 35, 1900) found his cultures still alive and virulent after seven or eight months.
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Of importance for the preservation of the life of the plague bacillus, is a low temperature. By maintaining cultures at a temperature of 20° to 25° C. the B. pestis may be kept alive and virulent for an extremely long and indefinite. period
of time.
My own results are confirmative of those obtained by the already mentioned investigators. I have kept the B. pestis alive from the end of one plague epidemic to the commencement of another. The organism grew on ordinary agar-agar and bouillon. On fluid blood serum, the length of life of the bacillus would appear to be long but very indefinite. No alteration in the virulence of the organism has been observed. Subcultures of the bacillus need not be made, provide the growths are kept at a low temperature. According to SCHULTZE, the length of life of the organism depends upon certain changes in the bacterial protoplasm.
In dealing with cultures of the plague bacillus it is of great importance ot know what virulence these possess.
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