Strictly speaking, this terrible scourge cannot be said to be in any sense a disease peculiar to warm climates, for the one climatic condition that appears to check the course of epidemics of this disease is extreme heat, which always moderates their virulence as long as it lasts. In reality, it is a disease of low civilisation; and appears to be practically incapable of attaining any serious spread amongst people of European habits. During the terrible recrudescence of this disease, which, for the last decade, has been ravaging the semicivilised world, although repeatedly introduced, it has never succeeded in seriously establishing itself in any European town. Even the admittedly backward sanitation of Spanish towns appears to be too advanced to admit of the spread of plague, and, what is more remarkable, the European portion of the population of plague-stricken Eastern towns has remained practically unscathed, while the indigenous population have been dying around them in their thousands. When first the disease invaded India there was naturally a good deal of alarm amongst the European population of Bombay, but nowadays the official, commercial, and social life of the European community goes on unmoved, even at times when the disease is doing its worst--and is so assured of its own immunity that timid ladies out for their evening airing will scarcely turn their head as the bodies of the plague-stricken are carried past them on the way to the burning ghaut. Perhaps this immunity may be to some small extent a question of race, but the main determining cause is undoubtedly difference of habits of life, as natives who have adopted European habits share in it. The most important conditions favouring the spread of plague appear to be overcrowding and inadequacy of air space and ventilation in dwellings; and especially lack of light, as well as the want of domestic cleanliness, and the treasuring up or neglect to do away with dirty rags, dust and rubbish. A further reason in India is the sacredness of animal life, which leads to the unrestricted multiplication of rats and vermin of all sorts.