_Causes._ Overloading of the rumen is especially common as the result of a sudden access to rich or tempting food to which the animal has been unaccustomed. Accidental admittance to the cornbin, breaking into a field of rich grass, clover, alfalfa, corn, sorghum, vetches, tares, beans, peas, or grain, or into a barrel of potatoes or apples will illustrate the common run of causes. A pre-existing or accompanying torpor or paresis of the stomach is a most efficient concurrent cause, hence the affection is especially common in animals debilitated by disease or starvation, but which have become convalescent or have been suddenly exposed to the temptation of rich food. For the same reason it is most likely to occur with food which contains a paralyzing element, as in the case of the following when they have gone to seed but are not yet fully ripened: Rye grass, intoxicating rye grass, millet, Hungarian grass, vetches, tares and other leguminosæ, and to a less extent, wheat, barley, oats and Indian corn. The same may come from the paralyzing products of fungi or bacteria in musty fodder or of such chemical poisons as lead, and the cyanides. A catarrhal affection of the rumen, and the congestion produced by irritant plants, green food with an excess of chlorophyll, and the whole list of irritants and narcotico-acrids, will weaken the first stomach and predispose to overdistension. Anything which lessens the normal vermicular movements of the rumen and hinders regurgitation and rumination tends to impaction, and hence an aliment which is to a large extent fibrous, innutritious, and unfermentable, such as hay from grass that has run to seed and been threshed, the stems of grasses that have matured and withered in the pastures, fodder that has been thoroughly washed out by heavy rains, sedges, reedgrass, rushes, chaff, finely cut straw, and in the case of European sheep, the fibrous tops of heather contribute to this affection. Lack of water is one of the most potent factors, as an abundance of water to float the ingesta is an essential condition of rumination. Hence pasturage on dry hillsides, prairies or plains, apart from streams, wells or ponds is especially dangerous unless water is supplied artificially, and the winter season in our Northern states, when the sources of drinking water are frozen over, and when the chill of the liquid forbids its free consumption, is often hurtful. Gerard attributes the affection to constant stabulation. This, however, has a beneficial as well as a deleterious side. It undermines the health and vigor, and through lack of tone favors gastric torpor and impaction, but it also secures ample leisure for rumination, which is so essential to the integrity of the rumen and favors the onward passage of its contents. With dry feeding and a restricted water supply it cannot be too much condemned, but with succulent food and abundance of water the alleged danger is reduced to the minimum.