Hoof-ail is probably propagated in this country exclusively by inoculation--the contact of the matter of a diseased foot with the integuments lining the bifurcation of a healthy foot. That it is propagated in some of the ways classed under the ordinary designation of _contagion_, is certain. That it may be propagated by inoculation, has been established by experiment. The matter of diseased feet has been placed on the skin lining the cleft of a healthy foot under a variety of circumstances--sometimes when that skin is in its ordinary and natural state, sometimes after a very slight scorification, sometimes when macerated by moisture; and under each of these circumstances the disease has been communicated. The same inference may be drawn, also, from the manner in which the disease attacks flocks. The whole, or any considerable number, though sometimes rapidly, are never _simultaneously_ attacked, as would be expected, among animals so gregarious, if the disease could be transmitted by simple contact, inhaling the breath, or other effluvium. The matter of diseased feet is left on grass, straw, and other substances, and thus is brought in contact with the inner surfaces of healthy feet. Sheep, therefore, contract the disease from being driven over the pastures, yarded on the straw, etc., where diseased sheep have been, perhaps even days, before. The matter would probably continue to inoculate, until dried up by the air and heat, or washed away by the rains. The stiff, upright stems of closely mown grass, as on meadows, are almost as well calculated to receive the matter of diseased feet, and deposit it in the clefts of healthy ones, as any means which could be artificially devised. It is not entirely safe to drive healthy sheep over roads, and especially into washing-yards, or sheep houses, where diseased sheep have been, until rain has fallen, or sufficient time has elapsed for the matter to dry up. On the moist bottom of a washing-yard, and particularly in houses or sheds, kept from sun and wind and rain, this matter might be preserved for some time in a condition to inoculate.