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In the cold weather a little pork is sometimes left over, but rather than have it left over it is sold the evening before at a reduced rate. This applies especially
to the markets other than the Central Market. This latter is the market where Europeans buy most of their fresh food, the others are used almost exclusively by
Chinese.
In the Central Market a little beef is sometimes left over, but is kept in consequence in ice chests.
That food material left overnight in shops and markets may be contaminated by excreta from rats must be borne in mind.
During 1904 thirteen rats from the Western Market (No. 7 Health District) were returned as being plague infected. Eleven such rats were also found at the Sai-ying-poon Market in No. 9 Health District.
Were food such an important factor in the causation of plague one would ex- pect the disease to be as prevalent amongst the well-to-do Chinese as it is amongst the poorer classes. The food supply for all classes of Chinese is from the same source and is very much of the same nature. The amounts of the ingredients of a meal vary with the purse of the consumer. Flesh, whether beef, pork, poultry or fish, is more largely 'caten of by the well-to-do classes, than it is by the poorer classes.
Yet it is always amongst the poor, living in the most overcrowded districts that plague is worst. This fact alone points to the different conditions under which the people live as a most important factor in plague incidence.
The infected food theory fails absolutely to explain the well established fact that the poor classes living under conditions of overcrowding, in cheap and often rat-ridden localities, with their beds, bedding and clothes often swarming with bugs and-fleas, should be more prone to plague infection than their more fortunate fellow citizens who can afford to live amidst more sanitary surroundings.
Infection via the Respiratory System.
On making post-mortem examinations of plague cases one is struck by evidences of general infection. For example one may frequently find the cervical, axillary, and inguinal glands to be enlarged, with minute haemorrhages, and to shew the bipolar staining organism on microscopic examination and yet to be discrete.
If one considers that given a skin iufection further progress must be via the lymphatics alone or that the virus of the disease on being carried to the nearest lymphatic gland must there necessarily be arrested, and that the bacilli do not gain entrance to the general circulation until the agonal period, one is then net by a difficulty in accepting the skin-infection theory as sufficient to account for the evidences of general infection.
This seems to me to be a too narrow view of the skin-infection theory.
The.Government Bacteriologist (op. cit., page 11) says that this is the pre- valent idea as regards bubonic plague. On turning, however, to the Report of the Indian Plague Commission, page 54, one sees septicemic cases described as cases "where owing to the more rapid passage of bacteria through the lymphatic filter, and possibly to a greater production of bacterial poisons, the constitutional symp- toms precede and overshadow the local symptoms, the disease being in most cas.s rapidly fatal."
It does not, therefore, appear to me that the supporters of the skin-infection theory have committed themselves to the narrow view which has been attributed to them.
However, some people have found difficulty in reconciling the skin-inf·ction theory with the post-mortem appearances, principally, it seems to me, on account of having accepted a too narrow view of the progress of a skin infection.
The infected-food theory having failed of acceptance as the usual channel except by a very small minority there has remained the theory of Respiratory in- fection for those who do not accept the skin-infection theory.