PLATE XV) SOME years ago one of us (J. G.), investigating the action of glycine on organisms of the coli-typhoid group, found that Bact. typhosum and Bad. paratyphosum A and B survived in a concentration of glycine which killed Bact. coli. An attempt to make practical use of this observation for the isolation of organisms of the typhoid group from faxes by adding glycine to various media was unsuccessful, probably because the margin between the lethal concentration for Bact. coli and those for Bact. typhosum and Bact. paratyphosum is too small. Examination of the growths of these organisms on agar in which 0.5, 0.75 and 1.0 per cent. of glycine had been incorporated revealed that these were of a sticky consistency and tenacious. Suspension in water was difficult and it was not easy to carry out slide agglutination. Microscopic examination of the organisms showed striking morphological changes. The bacilli were enlarged and markedly thickened and swollen. Subculture of the organisms from the glycine agar to ordinary nutrient agar, however, restored the normal colonial and morphological characteristics even after a dozen successive subcultures on glycine agar.More recently it was decided to extend the study of the action of glycine to other types of organisms. Whilst most of those investigated, and particularly the bacillary forms, showed degenerative changes, it was found that those of the cholera group revealed the phenomenon most strikingly and most constantly. Degeneration or involution forms have been recognised in the genus Vibrio for very many years and some of the early workers have described the occurrence of large spherical types. Mackie (1929) in the System of bacteriology has summarised the position by saying (p. 349) that " V . choleroe is undoubtedly polymorphic in artificial culture, and particularly in old cultures or in media to which certain antagonistic substances have been added ". GamalBia (1900, quoted by Lohis, 1922), Maassen (1904, quoted by Lohnis) and Hammer1 (1906) describe the production of large spherical 83
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