( 670 ) 
forms of bacteria, only with this deviation that towards the end 
the velocity of reaction was decreasing, instead of remaining constant. 
On the score of her experiments she is inclined to attribute this 
deviation to a difference in resistance between the individuals of 
various ages in the same culture. There would exist, as it were, an 
old and a young generation by the side of each other, the latter of 
which dies off slowest. Such a difference in connection with the age 
does not exist in spores to the same degree. 
Of the curves published by me, it is, however, not only the tail, 
but also the head that shows a deviation. The course is here, still 
apart from the incubation, much slower than according to the 
formula. At the most the middle part is, stating roughly, in accord- 
ance with it. 
Meanwhile it seems to me that this kind of investigations is hardly 
fit for a mathematical treatment. ; 
MADsEN & Nyman, for example, avail themselves of means, resulting 
from numbers of three values found, which deviate 25°/, and more 
from these means. 
An example from many *): 
found: 193, percentage of the average: 74.5 
330, 5 ee jn 127.4 
ka. WO, iy eae a 98.1 
average: 259 100 
And if the numerical results of Miss Crick are looked at somewhat 
more closely, they, too, do not appear to be more exact. Sometimes 
the errors in the observations are so great that, instead of the expected 
gradual decrease, here and ihere an increase of the number of 
survivors was in course of time to be noted’). 
It may be called objectionable, as Mapsen & Nyman do, to rid 
oneself of the deviations between the numbers determined experiment- 
ally and those calculated according to the formula, by remarking: 
‘Wenn man die grossen Versuchsfehler, die an dieser Art von Unter- 
suchungen kleben, in Betracht nimmt, ist die Uebereinstimmung eine 
recht gute’. It is true, a line may be drawn between a number 
of points determined experimentally, leaving one point to the left, 
another again to the right, but when, as is not very seldom the case 
here, the deviations from the regularity are considerable, imagination 
and arbitrariness will get too large a scope to inspire confidence in 
the correctness of a curve construed in this way. 
2 
Haler Table XI: 
1. e. Table III and X, 
9 
x 
