“…From the foregoing, one must conclude that the different colony forms of the diphtherial organism can not be differentiated definitely by qualitative differences in the usual fermentation tests. The clinching evidence for this decision would be metabolic studies with suspensions of the bacterial cells, and so far as the author is aware the only metabolic studies planned to clarify this point have been those of Passmore (1938) and Knox and Passmore (1938). The latter workers found that there is no significant difference between the oxygen consumptions per hour per mg. dry weight of bacterial suspensions of types mitis and gravis when employing glucose or glycogen as the substrate.…”