CONTAGIOUS AS WELL AS INFECTIOUS.

Experience has proved that plague can be transmitted from one person to another by direct contact; when a case of plague occurs in a house, other inmates of the house are much liable to be attacked also. Visitors to the house, medical and other attendants are also liable to be seized or to carry with them fresh focus of infection. It was, however, found in the Hongkong epidemic of 1894 that none of the European medical men, some fifteen in number, nor any of the Chinese students who were on duty at the plague hospital died. During the Egyptian epidemic of 1835 a French doctor, Bulard, with the courage of his conviction that plague was not contagious wore the shirt of a patient who died from plague, and yet did not contract the disease. Such immunity, however, was probably due to some circumstances which might be easily explained. In the Hongkong epidemic of 1894 three Japanese medical men contracted the disease, and in 1896, some European nurses were attacked. In Bombay the sad deaths of Surgeon-Major Manser and Miss Joyce prove that contagion plays an important part in the spread of the disease.

It has been maintained that plague is a miasmatic or soil-bred disease, and that the germs find in earth, water or in some form of fermenting or decomposing material a suitable nidus for growth. In this sense it is like malaria, which is endemic in a particular suitable area appearing and disappearing according as climatic or other conditions are favourable or unfavourable. The Chinese have a peculiar idea of the infection of plague. 12 They consider that the plague rises from the soil and believe that it first attacks small animals with breathing organs near the soil, such as rats, then animals with breathing organs a little higher, such as poultry, pigs, dogs, goats, cows, so on till it reaches man, whose breathing organs are higher from the soil than those of other animals.

The rats are undoubtedly attacked with plague before and during its prevalence among human beings, and they play an important part in the spread of its infection. In Kumaon this rat plague was observed by the people, and was recognized as a forerunner of the plague. The Times of India, September 30th, 1896, contains the following:—“It was known more than a month ago to all the people of Mandavi and to all the municipal sweepers in the district that the rats were dying in thousands all over the districts. They were found dead and dying almost everywhere, and in places where dead rats were never found before.” In Bombay an instance has been reported of a man trampling with bare foot on a rat which was seen slowly passing in a room and getting attacked by the plague soon after. Pigs, dogs, snakes, and jackals are said to be also affected by the plague. It will be seen that flesh-eating animals are the sufferers, due evidently to their eating plague flesh. Snakes swallow rats, and rats become infected by consumption of poisoned material or from infected soil or by their cannibal habit. Like other diseases due to a specific germ, the infection of plague may be caught from various sources such as the following—(a) By means of breath. Plague dust and dirt 13 are very potent infective agents. A man getting a whiff of dust from the floor of a room in which there is a plague patient blown into his face may get the infection. Sweepers and others engaged in conservancy are, therefore, easily attacked. (b) By food or drink. Grain adultered with sand or earth infected by rats may be a source of infection. Food may also be infected by flies or diseased rats (c) By direct inoculation through any abrasion in the skin or mucous membrane. People with bare feet are, therefore, more liable to catch the infection. The infection may be spread by infected linen, bedding, furniture and fomites. The discharge from buboes contains the germs, and is, therefore, highly poisonous. The fæces, the urine, the sputum, the fur on the tongue are also infective. If the theory be true that the poison attaches itself to the soil, then persons living on ground-floor are more liable to the infection, and a floating population less so. Dust laden with germs is the principal agent in the diffusion of plague as that of any other germ disease. Professor Aoyama of Tokyo, whilst making a post-mortem examination, scratched the left third finger and was attacked with the plague, also Dr. Ishigami, assistant to Kitasato.