DEVELOPMENT AND SCOPE OF BACTERIOLOGY 7 



relapsing fever. It is not surprising that the successes attained in these 

 diseases, fostering hope of analogous results in all other similar condi- 

 tions, but without the aid of adequate experimental methods, should 

 have led to many unjustified claims and to much fantastic theorizing. 

 Thus HaUier, at about this time, advanced a theory as to the etiology 

 of infectious diseases, in which he attributed all such conditions to the 

 moulds or hyphomycetes, regarding the smaller form or bacteria as 

 developmental stages of these more complicated forms. Extravagant 

 conjectures of this kind, however, did not maintain themselves for any 

 length of time in the light of the critical attitude which was already 

 pervading bacteriological research. 



Progress was made during the years immediately following, chiefly 

 in the elucidation of suppurative processes. Rindfleisch, von Reckling- 

 hausen, and Waldeyer, almost simultaneously, described bodies which 

 they observed in sections of tissue containing abscesses, and which they 

 believed to be microorganisms. Notable support was given to their 

 opinion by similar observations made upon pus by Klebs, in 1870. In 

 view, however, of the purely morphological nature of their studies, the 

 opinions of these observers did not entirely prevail. Satisfactory 

 methods of cultivation and isolation had not yet been developed, and 

 Billroth and his followers, with a conservatism entirely justified under 

 existing conditions, while admitting the constant presence of bacteria 

 in purulent lesions, denied their etiological significance. The contro- 

 versy that followed was rich in suggestions which gTeatly facilitated 

 the work of later investigators, but could not be definitely settled until 

 1880, when Koch introduced the technical methods which have made 

 bacteriology an exact science. By the use of solid nutritive media, the 

 isolation of bacteria and their biological study in pure culture were made 

 possible. At about the same time the use of anUin dyes, developed 

 by Weigert, Koch, and Ehrlich, was introduced -jito morphological study 

 and facilitated the observation of the finer structural details which had 

 been unnoticed while only the grosser methods employed for tissue 

 staining had been available. 



With the publication of Koch's work, there began an era unusually 

 rich in results held in leash heretofore by inadequate technical methods. 

 The discovery of the typhoid bacillus in 1880, of the bacillus of fowl 

 cholera and the pneumococcus in the same year, and of the tubercle 

 bacillus in 1882, initiated a series of etiological discoveries which, ex- 

 tending over not more than fifteen years, elucidated the causation 

 of a majority of the infectious diseases. 



