Report on the Bacteriology of Water. 4(55 



when the filaments are 20 fi long, the other not until the eighth 

 hour (8 P.M.), when 320 /t long. The first will grow at maximum 

 rate, or nearly so, for the first hour, and the filaments double their 

 length twice during that time, therefore = 80 p long (at 7 P.M.), and 

 then begin to decline ; the second will also double twice in the hour 

 (i.e., at 9 P.M.), and therefore be 1280 fi long when growth commences 

 to decline. 



Suppose during the second hour at 30 C. the doubling period is 

 twice as long as during the first hour, then the first culture will have 

 its filaments 160 fi long, and the second one 2560 /i long at the finish 

 (8 P.M. and 10 P.M. respectively). If during the third and fourth 

 hours the period is again doubled, the first culture at the end of the 

 fourth hour (10 P.M.) is 320 /t long, while the second culture (at 

 12 P.M.) is 5120 ft, and so on. 



If both had remained at 22 C., and maintained a doubling period 

 of, say, thirty minutes through the whole time regarded above (as 

 experiments show would be more or less the case), then, supposing 

 20 ft to be the length at starting (6 P.M.), it would be 320 /t at the 

 end of two hours (8 P.M.), and 1280 fi at the end of the next hour 

 (9 P.M.), corresponding to the first hour at 30 above, 5120 ft at the 

 end of the next hour (10 P.M.), and 81,920 /t after two hours more 

 (i.e., 12 P.M.). 



That is to say, at the more favourable temperature of 22 C.* the 

 filaments would attain a length of 81,920 fi in the same time as they 

 take to reach 5120 /*, or even 320 ft, if their last four hours or so are 

 spent at the higher unfavourable temperature. 



No doubt the ideal case given could not be actually realised, but 

 there can be no question that an approximation to it is what occurs, 

 and the matter resolves itself into this : At temperatures above the 

 optimum the organism cannot get as much out of the nutrient 

 materials as it can at temperatures near the optimum or below it, 

 evidently because there is some more or less enormous waste of energy 

 expended in doing something which no longer contributes to the 

 nutrition of the protoplasm, and this the more the higher the tem- 

 perature. To say that the respiration is rendered too intense in 

 proportion to the constructive metabolism is, no doubt, true, so far 

 as it goes ; but this does not explain the probably complex matter 

 beyond a certain as yet unsatisfactory point. 



There is one aspect of the matter worth noting. I imagine no 

 physiologist would allow that the destructive waste of energy going 

 on here has its seat solely in the food-materials, but would agree that 

 it is in the protoplasm of the ceil ; this is of importance, because we 

 must conclude that some presumably similar waste of energy goes on . 



* 22 C. is chosen because it was conveuient to work with, as being that used ; 

 but 25 C. is nearer the optimum. 



