652 Proceedings of the Royal Society of Edinburgh. [Sess. 
(b) In curve 2. The broth was heated to 37° C. prior to inoculation. 
Tube placed in the air of the incubator. No external precautions 
taken. 
(c) In curves 3, 4, 5, as in (6), but in addition the tubes were placed 
in a water bath in the incubator, and during manipulation, bath 
and tubes were removed, the tubes being kept as much as possible 
in the water bath. 
(d) In curves 6 and 7. As in (c), but in this instance two water baths 
were used, one in the incubator, the other outside of it. The tubes 
were manipulated in the second water bath, which was also 
kept at 37° C. 
(e) In curve 8. The same precautions were taken as in (d ) : the culture 
used for inoculation had been incubated for fourteen days. 
We found, then, that by adopting the procedure as stated in (d), and by 
using for inoculation only actively growing organisms from very young 
cultures, the latent period was entirely eliminated (as is shown in curves 
6 and 7). 
The figures of curves 3, 4, 5, 6, 7 are given on the opposite page. 
[Note . — It will be noted that in curves 4 and 5 the latent period was 
still in evidence.] 
We return to the mathematical theory. 
Equation (2) c ^M. = by (a — y) 
CiZ 
becomes on integration 
(3) y = 
1 ■ a- Vo e -«w 
Vo 
where y 0 is the value of y at the time t = 0 , i.e. the number of organisms 
originally inoculated, and a and b are constants to be determined. 
When A 
at 
0 (i.e. when multiplication has ceased) 
y = a. 
Enumerations beyond this point give irregular results ; the samples taken 
are uneven, probably on account of clumping. 
From a study of the manner in which the curves flatten after eight 
or nine hours’ growth, a suitable value of a may be inferred in each 
case. 
