the point of inoculation is inflamed and infiltrated with a bloody, gelatinous exudate. The spleen is enlarged and sometimes the lymphatic glands are swollen. The bacillus is found in the blood and in all the organs.
Mice and guinea pigs fed with pure cultures or with tissues containing the germs die with the symptoms mentioned above. Kitasato found the bacilli in a dead mouse from a plague-stricken house. He also inoculated animals with dust gathered from such houses, and one of these died with symptoms of the plague, and the bacillus was found in its body. In certain parts of Asia the disease is, according to Cantline, known as "rat plague," thus indicating an extensive infection of these animals.
Cantline makes the following statement concerning the susceptibility of rats to the disease: "On all hands rats are reported to behave peculiarly and with a wonderful constancy. Before, or it may be during an epidemic of plague, or before the individuals in any particular house in an infected locality are stricken, the rats leave their haunts and seek the interior of the house. They become careless of the presence of man, and run about in a dazed way with a peculiar limping jerk or spasm of their hind legs. They are frequently found on the bedroom floor or on the tables, but not infrequently their death is known by the putrefactive odor of their decomposition arising from beneath the flooring. So pertinent has this rat affection become, that during the epidemic in Macao in 1895 the Chinese and Portuguese left their houses when the diseased rats invaded their premises. The cause of the rats' behavior is undoubtedly disease, and the symptoms tally wonderfully with plague symptoms of man. Dr. Rennie examined them carefully in Canton, and noted the following post-mortem appearances: (1) The stomach was distended and filled with particles of food, sand, and indigestible substances, and the mucous membrane was red and inflamed toward the pyloric end; (2) the liver was much enlarged and congested, and contained ova of tænia and distoma; (3) there was congestion at the base of the lung present in about forty per cent; and (4) glandular enlargement was present in thirty per cent of those examined. There is no doubt now that the disease in the rat and man is identical. The bacillus of plague has been met with in every case of rat disease of this description when it has been searched for. The infection of the rat is raised from being a mere popular belief into one of scientific precision, and we must now accept the rat, at any rate, as one animal liable to the plague. Whether the rat is affected previously to, coincidently with, or subsequently to man being attacked is open to question. Is the disease among rats a forerunner of its outbreak in man, and, if so, are they a means of infection? These are, of course, two separate questions."
