This climatic influence, however, is probably not responsible for more than fifteen or twenty per cent of all cases, and, popular impression to the contrary notwithstanding, the liability of outdoor workers who are subject to severe exposure, such as lumbermen, fishermen, and sailors, is only slightly greater than that of indoor workers. The highest susceptibility, in fact, not merely to the disease, but also to the development of serious heart involvements, is found among domestic servants, particularly servant girls, agricultural laborers and their families (in districts where wages are low and cottages bad), and slum-dwellers; in fact, those classes which are underfed, overworked, badly housed, and crowded together. Diet has exceeding little to do with the disease, and, so far from meat or high living of any sort predisposing to it, it is most common and most serious in precisely those classes which get least meat or luxuries of any sort, and are from stern necessity compelled to live upon a diet of cereals, potatoes, cheap fats, and coarse vegetables. Even its relations to the weather and seasons support the infection theory. Its seasonal occurrence is very similar to that of pneumonia,--rarest in summer, commonest in winter, the highest percentage of cases occurring in the late fall and in the early spring; in other words, just at those times when people are first beginning to shut themselves up for the winter, light fires, and close windows, and at the end of their long period of winter imprisonment, when both their resisting power has been reduced to the lowest ebb in the year and infections of all sorts have had their most favorable conditions of growth for months. The epidemics of rheumatism, which occasionally occur, probably follow epidemics of influenza, tonsillitis, or other mild infections, and instances of two or more cases of rheumatism in one family or household are most rationally explained as due to the spread of the precedent infection from one member of the family to the other. Instances of the direct transmission of the disease from one patient to another are exceedingly rare.