VIABLE BACTERIA IN YOUNG CULTURES 



419 



sion up to one in thirty-two. A three and one-fourth hour broth 

 culture at 37°C. of Bad. suipeslifer was used for counting and 

 dihitions wore put up ahiiost sinuiltancously in the six fluids at 

 hand. Viable counts were conducted at the start and thereafter- 

 wards at intervals up to 49 hours. In all cases the counts were 

 performed under strictly comparable conditions. The results are 

 shown in table 3, the counts being given in terms of the original 

 culture . 



Neglecting the slight irregularities in the series, which were 

 probably due to small differences in the dropping pipettes used — 

 this experiment being performed before a micrometer had been 

 obtained for checking their caliljration — it is at once clear that 



TABLE 3 



up to twenty-one hours the 1 : 16 dilution of Ringer's solution is 

 no more harmful to the bacilli than the pure solution. But be- 

 tween the 1:16 and the 1:32 dilution there is an enormous dif- 

 ference; the latter acts just like distilled water, rendering the 

 emulsion sterile within twenty-four hours. From this it may be 

 inferred that a minute but quite definite amount of various kinds 

 of salts is necessary to prevent the deleterious action of distilled 

 water. WTiat particular quantities of what particular salts was 

 not entered into more fully, as it lay outside the scope of tliis 

 work. The practical conclusion to be drawn from these experi- 

 ments seems to be that in preparing dilutions for a viable count 

 on a bacterial culture, the best fluid to use, so far investigated, 

 is undoubtedly Ringer's solution; particularly is this the case if 

 the emulsions have to be kept for some time, or possibl}^ shaken, 

 before the actual agar is inoculated. If the tubes are to be put 



