PARAMECIUM IN PURE CULTURES OF BACTERIA 429 



The bacteria taken from the plates were secured in pure cul- 

 ture and maintained on agar slants in test tubes. From these 

 slants their morphological and cultural characteristics were de- 

 termined. In every case the examination was carried far enough 

 to secure a good idea of the general character of the organism. 

 Their shape (whether rod, coccoid, or spiral), size and motility 

 were determined in every case. Tests were made for spores by 

 subjecting them to a temperature of 76°C. for twenty minutes. 

 Their reaction to stain was tested with methylen blue carbot 

 fuchsin, and Gram's stain. Their general cultural characteristics 

 were determined as follows ; agar was used to determine the kind 

 and amount of growth ; beef broth for an examination of motility 

 and the test for indol; litmus milk was used to show whether 

 the organism produced acid, and whether it produced a coagula- 

 tion and saponification; in dextrose fermentation tubes was ob- 

 served the power of fermentation and gas production; gelatin 

 stab cultures were made to determine whether the organisms 

 could liquefy the medium, and to show the general character of 

 growth. In some cases other media were used, such as lactose 

 broth, hay infusion agar, potato. 



Having secured a good description of each culture they were 

 identified, so far as possible, by using Chester's ''Manual of 

 Determinative Bacteriology." In some cases the identification 

 was exceedingly difficult, since the description of these sapro- 

 phytic bacteria is incomplete. One or two of the bacteria iso- 

 lated and used for experimentation could not be identified by 

 name. 



In the analysis of abnormal hay infusions several protozoan 

 cultures, formerly rich in Paramecium, were found in which fer- 

 mentation and putrefaction were in progress and in which Para- 

 mecium and other infusoria were either absent or few in number 

 and not in vigorous condition. Materials from six such cultures 

 were plated and pure cultures of the bacteria obtained in the 

 same way as for the normal infusions, and their morphological 

 and cultural characteristics determined. A very large number 



