is also due to intoxication with a protein toxin produced by bacteria of the genus Clostridium. These bacteria and their spores and ubiquitous, and the majority of them do not produce neurotoxins. The selective advantage of producing such potent toxin is still a matter of speculation (see Popoff, this volume). The next major advance was the discovery that tetanus neurotoxin 1 can be converted by formaldehyde treatment to a nonpathogenic but still fully immunogenic form, and that this can be used successfully as a vaccine to prevent tetanus (RAMON and DESCOMBEY 1925). Similar vaccines (toxoids) can be prepared with botulism neurotoxins (see MiDDLEBROOK and BROWN, this volume). The prevention oftetanus by vaccination (see Galatzka and Gasse, this volume) is one of the great successes of basic research coupled with an efficient public medicine service.