635 
of his supposition, shows only how a geometrical series can come 
forth, not however why it always must do so, for example in the 
case of anthrax spores. in spite of varying conditions of growth. 
This points to a regularity as to the age-distribution, which of itself 
requires an explanation. In my opinion, the one put forward by 
REICHENBACH is inadequate. 
It would seem then that, if we have to find an explanation, the 
only way would be to consider the progress of disinfection to be 
mainly a physico-chemical phenomenon. Mapsren and Nyman and 
Cuick lend further support to this view by agreeing that van ’r Horr’s 
temperature coefficient appears to be applicable in this case. 
It may indeed be called in question, whether this material allows 
of a mathematical treatment, since it can hardly be worked with 
without committing serious experimental errors. Consequently, as I 
pointed out in my first paper, the experimental data of the researchers 
just mentioned, were far from accurate. Their results however, having 
been corroborated by several other observers, their opinion that the 
process of disinfection exhibits some analogy to a unimolecular 
reaction, can no longer be disputed. Setting aside experimental errors, 
divergencies from the regular process should then be ascribed to 
individual differences in resistance. 
b. Bacillus coli. 
It seems that the individual differences mentioned above are more 
frequently displayed by vegetative forms than by spores, anyhow 
they show many more departures from the regular process. 
H. Cuick found no less than three types of the curve of survivors 
for the disinfection of staphylococcus pyogenes aureus with hot 
water. I also refer to Figs. 2 and 3, giving the logarithmic curves 
for the disinfection of bac. coli respectively by heat and with 0,5°/, 
phenol. It will be seen from Fig. 2 how three coli-cultures A, B 
and C, though taken from the same stock, when killed by heat, 
yield very different types. B is the only one that corresponds with 
the type of the unimolecular reaction. C shows a marked departure, 
A only a slight one in the opposite direction. 
In order to give an idea of the degree of acenracy of this kind 
of investigations I once more subjoin all the quantitative results of 
an experiment in Table II. We know that plate-culture is not a 
very precise quantitative method. Sets of parallel cultures not seldom 
yield essential differences, even though the sampling may have been 
