( 673 ) 
Bac. coli 
70009 
00 
a ea : 
g 800 Sui eS 
ee. Ge 3 
=" 600 _ 8 
2 Be 
ad Bd x 
se ge 5 
00 5 
aal 3 
Bit ee wd z 
5 0 Cs ® 
Minutes 
Fig. 2. 
As in our former experiments, when the bacteria were killed by 
heat, we now also experienced, while using phenol as a disinfectant, 
that, though cultures of one stock are used at every time, yet we did 
not succeed in coming to somewhat equal results. This is taught by 
a look at fig. 1, in which a number of eight curves have been drawn, 
referring to experiments, made at different times each with fresh 
cultures of the same colistock. The concentration of the phenol and 
the temperature at which the disinfection took place, were in all 
cases the same and yet for the greater part quite different curves 
were obtained. 
Bac. coli 
1000 Wee 
Rn A 
A La Neha desta rolde 
eee 
en : 
Boole EE FE El Sa a 
° Ps ede fe eae a ak [bn & 
Ss 4500 3 A 
— a TS SE Ss ve 
= 400 } 
ESR | 
O0 rea 0 En 5 
Eed ae EEN ea zE 
el 0 Pore ei 8 
x 0 2 4 6 8 10 1214 16 18 20 
Minutes 
Fig. 3. 
Owing to this, it will not do merely to compare the results of 
one experiment with those of another, unless both are made with 
the same culture and about the same time. Therefore strictly speaking 
parallel experiments are necessary, if one wishes to study the influ- 
