_Bacteriology._--The cause of botulism poisoning was discovered by Van Ermengem to be the toxin produced by a bacillus which he named _B. botulinus_. This organism was isolated from portions of a ham that had caused fifty cases of poisoning (1895) at Ellezelles (Belgium), and also from the spleen and gastric contents of one of the three fatal cases. The bacillus grows only in the absence of oxygen (strict anaërobe), stains by Gram's method, forms terminal spores, and develops best at 22°C. Unlike most bacteria dangerous to man, it appears unable to grow in the human body, and its injurious effect is limited to the action of the toxin produced in foodstuffs outside the body. Botulism is an intoxication--not an infection. The fact that the bacillus can grow in nature only when the free oxygen supply is cut off explains in part at least the relatively rare occurrence of botulism since all the conditions necessary for the production of the botulism toxin do not commonly concur. Next to nothing is known as to how widely _B. botulinus_ is distributed. Except in connection with the cases of poisoning it has been reported but once in nature.[108] The botulism poison is a true bacterial toxin, chemically unstable, destroyed by heating at 80°C. for 30 minutes, capable of provoking violent symptoms in minute doses, and possessing the property characteristic of all true toxins of generating an antitoxin when injected in small, non-fatal doses into the bodies of susceptible animals. In animal experiments the toxin formed by _B. botulinus_ has been found capable of reproducing the typical clinical picture of this form of food poisoning. Symptoms of paralysis are produced in rabbits, guinea-pigs, and other animals by the injection of so small a dose as 0.0001 c.c. of a filtered broth culture. [Illustration: FIG. 11.--_Bacillus botulinus_ with spores. Pure culture on sugar-gelatin. Van Ermengem preparation. (Kolle and Wassermann.)]