DEVELOPMENT AND SCOPE OF BACTERIOLOGY 7 



the bacilli he had found. This, in a crude way, expresses the modern 

 conception of infectious disease. 



Within a few years after this, 1868, the adherents of the parasitic 

 theory of infectious diseases were further encouraged by the dis- 

 covery, by Obermeier, of a spirillum in the blood of patients suffering 

 from relapsing fever. It is not surprising that the successes attained 

 in these diseases, fostering hope of analogous results in all other 

 similar conditions, but without the aid of adequate experimental 

 methods, should have led to many unjustified claims and to much 

 fantastic theorizing. Thus Hallier, at about this time, advanced a 

 theory as to the etiology of infectious diseases, in which he attrib- 

 uted all such conditions to the molds 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 re- 

 search. 



Progress was made during the years immediately following, 

 chiefly in the elucidation of suppurative processes. Rindfleisch, von 

 Recklinghausen, 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 pre- 

 vail. 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 con- 

 stant presence of bacteria in purulent lesions, denied their etiological 

 significance. The controversy that followed was rich in suggestions 

 which greatly facilitated the work of later investigators, but could 

 not be definitely settled until 1880, when Koch introduced the tech- 

 nical 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 anilin dyes, developed by Weigert, Koch, and 

 Ehrlich, was introduced into 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. 



