THE SCIENCE of sanitary wat,er bacteriology began in 1880 when von Fritsch described Klebsie7la pneu-monia and K. rhinoscleromatis as organisms characteristic of huiman fecal contamination. A short time later Escherich identified Bacillus coli as an indicator of fecal pollution. Botth observers considered human fecees as dangerous pollution wlhile the feces of other warm-blooded animals we're not so regarded. From this origin the current "coliform group" developed to include numerous micro-organisms of diverse biochemical and serologic cha,racteristics, natural sources and habitats, as well as controversial sanitary interpretations. Investigators continued to enlarge the number of organisms classifieid within the coliform group by applying all available physical and biochemical procedures. In 1908, Bergey and Deehan (1) expandeld the classification to include, 16 groups composed of 256 types. The difficulties associated with application of so many subdivisions caused Jackson (2) to propose classification into only 16 groups based on sucrose, dulcitol, raffinose, and mannitol fermentation. A tremendous amount of information was available on the physical and biochemical characteristics of the coliform group, but the correlation between the source of the various types, such as fecal, vegetable, and soil, and these tabulated characteristics left much to be desired in sanitary interpretation.