A soluble specific substance in spirochætes

In the differentiation and recognition of the various species of spirochætes morphological and biochemical methods of study give such limited assistance that there is every inducement to investigate more fully the serological relationships of these organisms. By use of the agglutination, complement fixation and adhesion tests, by the use of Pfeiffer's phenomenon, and by a study of active immunity against infection, much information has already been obtained. With the ultimate object of adding to the differential tests in vogue we have begun a search in certain of the more easily cultivated types of spirochætes for soluble, specific, serologically active substances comparable to those which have now been isolated from many bacteria. The greatest initial difficulty has been to cultivate the organisms in sufficient amount to allow of the extraction from them of any appreciable quantity of a reactive substance: the culture of spirochætes in bulk is a very different problem from that of growing them in a few test tubes.