SEA-FISHERIES LABORATORY. 



Experiment III. 



131 



Days. 



1 



2 



3 



4 



5 



6 



7 



No. of bacteria per 1/1000 c.c. 

 1/100 c.c.... 

 1/50 c.c. ... 



1 c.c 



„ ,. 5 c.c 



30 



37 



5 







"3 



1 







The experiment was now discontinued. 



A further experiment was made with the object of checking 

 the original one. A similar culture to that employed above 

 was used, but in a different manner. A fresh culture on nutrient 

 agar was made from the stock culture (which had been kept 

 for several months), and a few c.c. of sterile broth having 

 been poured into the tube the culture was rubbed up into the 

 liquid so as to make an emulsion of the bacteria. About 

 1 c.c. of this emulsion was then added, as before, to about half 

 a litre of sterile sea- water contained in a flask, kept as before. 

 The number of bacteria in the culture was estimated from 

 day to day with the following results : — 



Experiment IV. 



Days. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



No. of bacteria per 



1/10,000 c.c. 



279 



319 



129 



58 



24 



32 



10 











„ 1/1,000 c.c. 

















45 



54 



11 





„ 1/100 c.c. ... 



... | .. 



















56 



Now, considering the first three experiments, we see 

 from these rough results that the number of bacteria per 

 unit volume of culture first of all undergoes a very rapid 

 reduction, and then the rate of reduction becomes very much 

 less. It is quite clear that a graph of these ungraduated 

 figures would show that the curve would fall asymptotically 

 close to the axis of y, and these would approach the axis of x 

 in the same way. 



