Outside the animal body the bacillus has a saprophytic life in rich garden mould, street dust, stables, yards and drains, and the cracks of floors. Nicolaier failed to obtain it in soil from forests and from the deeper layers of garden earth. Marchesi found it to a depth of two metres but no more. Again it is much more abundant in tropical countries than in temperate and cold ones, and appears to be to a great extent limited to particular localities. It has been found in the intestinal contents of man and horse (Babes, Sormani), and in horse manure, and this mingling with the surface soil and generating an abundance of ammonia determines the anærobic conditions which favor the growth of the microbe. This serves to explain the remarkable prevalence of the disease among those living or working about stables, gardeners, agricultural laborers, soldiers on campaign, and children and others walking with bare feet. The contact with rich infected soil greatly favors inoculation in any accidental wound. An important feature in the pathology of tetanus is that the bacillus is confined to the seat of the inoculation wound. The many attempts to transmit the infection by blood, nervous matter, and by one or other of the tissues have uniformly failed, though the pus of the infected wound has proved virulent. Similarly, the attempts of Kitasato and others to obtain cultures from the animal liquids or tissues apart from the wound have been futile. By inoculating the toxins remaining in the pus of the infection wound, however, or in virulent cultures from which the bacilli have been removed by filtration or in which they have been destroyed by heat, all the symptoms of tetanus can be produced (Kitasato, Kund Faber, etc.) In such cases too, the symptoms appear at once, as soon as the toxin is absorbed, and not after a definite period of incubation as in inoculation of the unaltered virus. Kitasato, Vaillard and Vincent reached this conclusion by another channel. They inoculated mice at the root of the tail with virulent tetanus cultures, and at definite intervals after, namely, half an hour, one hour, and one and a half hour, they made a circular incision round the wound and thoroughly cauterized the whole, thus destroying all the inoculated bacilli. They found that tetanus was prevented in those animals only which were operated on at the first half hour. Again, Kitasato injected mice with 0.2 to 0.3cc. of the blood from the heart of a fresh tetanus cadaver, and thereby produced typical tetanic symptoms and death in 1 to 3 days.