_Accessory Causes._ These are especially those conditions which favor the transmission of the germ from animal to animal. They include the reprehensible habit of allowing swine to run at large so that herd mingles with herd; the freedom to wander along the lines of railroad by which hogs are carried, and where the infected excretions fall on the ground; the scattering of infected litter or manure from a car or boat; the use of the same cars, boats or trucks for the conveyance of infected and sound pigs in succession, without intermediate disinfection; the use of the same loading banks, chutes, runways, yards, pens and feeding and watering troughs by strange pigs from all sources in succession, without constant disinfection; the purchase of stock swine at public markets; the return of swine from public fairs and exhibitions; the feeding and watering of pigs on the line of streams that have drained pig pens or pastures higher up; the use for pigs of premises that have harbored infected ones at an earlier (even distant) date; the supply of food or litter from barns where pigs have recently died; the admission to the pens or yards of butchers, dealers or others who are likely to carry infection on their persons; the admission even of wagons, dogs or other animals, including birds, tame and wild, which are liable to carry infection. Of all birds the buzzard is the most to be shunned as having presumably just come from infected carrion, but barnyard fowl and small birds that feed from the same trough with the pig are to be feared as well. The same remark applies to rats and mice, squirrels, skunks, woodchucks and rabbits which may easily carry the infection on their paws. If the infection is near, flies and other insects, in the warm season, will convey it for some distance from herd to herd. A common cause is the feeding of swine about abattoirs where they devour the offal and waste in a raw condition. Another is the feeding of boarding house, hotel or other kitchen slops, raw, or without the most exhaustive precautions in the way of cooking. Many outbreaks can be traced in this way to the consumption by the animals of the products of infected swine. Some indeed are fostered by the utter neglect of the parties in charge of an infected herd, in leaving the infected carcasses exposed so that they are eaten by wandering hogs, or portions are carried away by buzzards, carrion crows, dogs and other animals. In some cases a strong wind will carry the infection on dust, straw or other light object into sound herds at a distance. The introduction into a hitherto healthy herd of an apparently sound pig may be the occasion of a deadly outbreak. The strange new pig may have already had the disease, and in a condition of immunity, may without hurt to itself, carry the germ which becomes so fatal to the susceptible.