This susceptibility is one of the most important factors. It may be inherent in a given family or strain of blood. It may be enhanced by a constitutional weakness, engendered by too close breeding, by breeding from the young and immature, or from the old and worn out. It may be favored by a general debility from starvation, faulty or injudicious feeding, as exclusive feeding on corn (maize), an unbalanced ration, feeding cotton seed, irregular feeding, etc. It may result from parasitism, as round worms in the lungs, bowels, muscles, fat, kidneys or liver, from trichinosis, from cysticerci, echinococci, or from distomatosis. These not only lessen the force of constitutional and phagocytic resistance, but they also in many cases open the way for the entrance of the microbe by the wounds which they inflict. Perhaps nothing operates more effectively in this way than the attacks of other pathogenic microbes. The treatment of the domestic hog is often such that it would almost appear as if it were designed to destroy health and vitality. He is used to clear up the soiled and spoiled provender which has been rejected by other animals. Decayed vegetables and flesh of all kinds, which is no longer fit for other use, is supposed to be good for him and is furnished raw. Worse still, this is conveyed in barrels that are never washed, but are sent for each new supply reeking with abominations which render them a nuisance on the highway. It is left standing till wanted in these barrels, or in still larger receptacles, which are never emptied nor cleaned, but are allowed in the hottest weather, to continue a hotbed of the foulest fermentations. On a smaller scale the kitchen swill barrel becomes a similar centre of decomposition. Even at the creamery and cheese factory the surplus or waste products often remain in a common tank breeding larvæ, toxins and ptomaines, before they are fed to the hogs. In the hog pen, or yard, corn in the ear is thrown on the ground, already filthy with the solid and liquid excretions and is eaten with the rotting, if not infecting, filth in which it has been rolled. From grubbing in this filth with his snout, the pig plunges the latter in the liquid food in his trough and too often he gets his feet into the food as well, and further charges it with the injurious ferments. Again the kitchen swill is liable to contain various inorganic poisons and notably the carbonates and bicarbonates of potash and soda which are used to excess in the form of _powdered soaps_ and, as shown by experiment, are deadly poisons to pigs.