The Microbic Dissociation of Hemophilus Influenzae *

Dissociation in both pathogenic and non-pathogenic bacterial species has long attracted attention, both in this country and abroad, and, as a result, a voluminous literature on the subject has been accumulating. Since the work of Arkwright' and of deKruif7 in I921, dissociational variations in the properties within a bacterial species have been studied in a more or less systematic manner so that at present most of these variations, particularly those intimately associated with cultural characteristics, cell morphology, biochemical reactions, virulence, and serological reactions, can be more or less controlled and predicted. The uncertainty which still surrounds this phenomenon, however, is clearly shown by the diversity of opinions with reference to its nature held by those who have studied the problem from various angles. In fact, at the present time no single explanation is applicable to all cases. Hadley5 admirably reviews the current conceptions of microbic dissociation and gives an excellent analysis of the general literature dealing with this subject. In all the more recent literature dealing with microbic dissociation, two distinct types of colony formation have been noted and described. These have been designated as the S, or smooth type, and the R, or rough type, according to whether or not the colony appears smooth or rough when grown on solid media. A stable form of the R-type of colony obtained as a variant from the S-type usually shows marked variations from its progenitor, particularly in colony formation, morphology, biochemical behavior, and virulence. However, such variations are not observed in all cases. Recently, many of the more commonly known organisms have been successfully dissociated by artificial means, and their resulting