The bacillus of tetanus is a somewhat slender, rod-shaped organism, with a peculiar tendency to spore formation at one end, which gives it a drumstick appearance. It is essentially an anaërobic organism, and can never be cultivated in contact with the air. In laboratory experiments it is grown in the depths of a solid culture medium or else in fluids and on surfaces in an atmosphere of hydrogen gas. It is one of the apparent contradictions of bacteriology that this organism, which can only be grown as an anaërobe, nevertheless abounds in earth, particularly the rich, black loam which best supports luxuriant vegetable life, and that it practically inhabits the upper layers of the soil, which accounts for the fact that so many contaminations and infections have occurred from stepping upon planks or boards with nails projecting, or from introduction of splinters, or from lacerations of the hands and feet which are so often followed by contact with such materials. There is nothing about a rusty nail wound which, by itself, predisposes to tetanus, but the rusty nail upon which a person steps is either itself infected or leaves a rent or wound which may become infected within the next few moments, and which is not likely to receive the careful attention which it should. Verneuil has of late laid stress upon the fact that in localities where horses are kept tetanus is more prevalent, and that the infectious organism abounds in and upon stable floors, about barn-yards, and wherever the excretions of a horse may be found. Bacteriologists are aware that in the intestines of herbivorous animals the bacilli (anaërobic) of tetanus and malignant edema are often found. Verneuil has further shown that almost the only instances of tetanus which occur on shipboard are upon those ships which are used for transportation of horses and cattle. His statements are at least interesting, if not absolutely well-founded. At all events, tetanus is certainly of telluric origin. A French veterinary surgeon of twenty-five years’ experience had not seen a single case of tetanus until 1884, when he “removed a tumefied testicle from a horse, with the _ecraseur_, and it died of tetanus; in the following six months he castrated five, and all died; another castrated fifteen in one day, and all died but one; another in ten days castrated six bulls and operated on three fillies for umbilical hernia, when five of the bulls and one of the fillies died.” This will illustrate how the infectious agent may be conveyed by instruments, etc.