These and other difficulties for many years delayed the final proof of the true pathology of tetanus. The success of the work was mainly due to Nicolaier. He started from the well-known fact that tetanus mostly comes of wounds or scratches contaminated with particles of earth--such mischances as the grinding of dirt or gravel into the skin, or the tearing of it by a splinter of wood or a rusty nail; as Dr. Poore says, in his Milroy Lectures (1899), "Every child who falls on the ground and gets an abrasion of the skin, all tillers of the soil who get accidental wounds in the course of duty, and every horse which 'breaks its knees' by falling in the London streets, runs potentially a risk of inoculation with tetanus." Nicolaier therefore studied the various microbes of the soil, and made inoculations of garden-mould under the skin of rabbits. He was able, by these inoculations, to produce tetanus in them; and the discharge from the points of inoculation, put under the skin of other rabbits, produced the disease again. He also identified the bacillus, and cultivated it; but in these cultures it was mixed with other organisms, and he failed to isolate it from them. Carle and Rattone, and Rosenbach, were able to produce tetanus in animals by inoculating them with discharge from the wounds of patients attacked by the disease. Finally, Kitasato, in 1889, found a way of obtaining pure cultures of the bacillus. Beginning with impure cultures such as Nicolaier had made, he kept these at a temperature of 36° C. till the bacillus had spored; then, by repeated exposures of the cultures to a temperature of 80° C. for three-quarters of an hour at a time, he killed-off all organisms except the spores of the tetanus-bacillus; then he kept these in an atmosphere of hydrogen, at a temperature of 20° C., and thus got pure cultures.