Report on the Bacteriology of Water. 423 



Normal doubling period : 



135270 n = 4.40 P.M. 5.17 P.M. - 37 minutes at 31 '2 31 '7 0. 



In resuming the foregoing series, we note that they fully bear out 

 the previous conclusions, and are closely comparable with the broth- 

 cultures. 



Before proceeding to summarise further, it will be instructive to 

 look at a series of experiments made not with spores, but with seg- 

 ments of filaments transferred bodily to the new media for measure- 

 ment. 



D. Experiments with Growing Bacilli and Filaments in Broth + 1 per 

 cent. Gelatine, and in Broth alone. 



On July 29 I tried the following experiment. Spores sown in 

 broth + 1 per cent, gelatine in a tube were kept in incubator till 

 5 P.M. at 25 C. Then I fused the tube end, and thoroughly shook up 

 the filaments to break them into segments. A drop was then used to 

 infect a new tube, and from this a drop put into a cell and used to 

 see if the growth measurements would correspond. 



An excellent rod, 24*75 /A long, was easily found in the drop at 

 5.7 P.M. Giving this a little time to recover the shock of the 

 violent shaking, and to accommodate itself to the temperature, 

 food material, &c., I proceeded to measure it, noting that it began 

 to grow at once, as follows : 



A very slow, but distinctly perceptible growth. 



The regular measurements were then begun at 5.30 P.M.. 



Normal doubling periods : 



1. 29 -2568 -5 >i = 6.30 P.M. 6.15 P.M. = 45 minutes at 2625 '826 0. 



2. 58 -5117 = 6.15 6.55 = 40 26 '026 -4 C. 



3. 117234 = 6.55 7.34 = 39 26 '426 0. 



It is clear that the rate of growth is the same, under the same 

 conditions, as for the filaments normally germinated out from the 

 spores, a point of some importance, as it may perhaps permit an 

 extension of the method in several directions, besides a considerable 

 saving of time. 



