The Salmonella Group. Definition and Classification. The genus Salmonella comprises gram-negative and non-spore-forming bacilli that, as a rule, are motile by means of peritrichous flagella, grow well on ordinary culture media, produce acid and gas from mannitol, maltose, glucose and sorbitol, do not ferment lactose, sucrose and salicin, do not form indole from peptone and do not liquefy gelatin. They have one common quality: “All the known species are pathogenic for man, animals or both” [White, 1929] (367). Though some of the types have not yet been isolated from man, it is fair to assume that all of them are at least potentially pathogenic for man. Because of the importance for human and veterinary pathology, there exists a need for a rapid and simple method of identifying cultures as belonging to the Salmonella group. No single criterion is available by which this can be done.