( 668 ) 
to carbon dioxide. These conditions will doubtless never be fulfilled 
in land plants, in water plants perhaps very exceptionally. 
It has therefore been established by Mr. Zisistra’s investigations, 
that the speaker was wrong when, in his above cited paper, he 
came to the conclusion, that a leaf or leaf fragment cannot form 
starch in a space free from carbon dioxide, when parts organically 
connected with it, or even immediately adjoining it, are placed in 
an atmosphere very rich in carbon dioxide. Mr. Zijrsrra’s results are 
however, in complete agreement with the main result, formerly 
obtained by the speaker, according to which the carbon dioxide of 
the’ soil, even if it should be absorbed by the roots, cannot appre- 
ciably contribute to the synthesis of organic matter in the leaf. 
Groningen, January 29%, 1909. 
Microbiology. — “/nwestigations on the subject of disinfection”. 
By Prof. C. ErkMan. 
Last year I communicated results of experiments ') from which it 
appeared that the resistance against high temperature of bacteria 
of the same pure culture is individually very different. While for 
example the majority die off in a few minutes, some may remain 
alive after ‘/,, */, hour, etc. If the times are noted on the absciss 
and the corresponding numbers of survivors are drawn to it as 
ordinates, we get as “curve of survivors” a line which in general 
has the form of a \. In a slow process, as it occurs when the 
mortal temperature is taken relatively low, the first part of the curve 
shows itself clearly as an horizontal line and therefore represents a 
latent stage of incubation. Notwithstanding this the period within 
which the first half dies off, is much shorter than the following, in 
which the second half passes away. 
In a quick process, as is observed when the temperature is far 
above the physiological limit, the duration of the incubation will 
become so brief that it easily escapes notice. In connection with the 
inevitable circumstance that the number of observations in this kind 
of experiments cannot be increased arbitrarily, but is confined within 
a rather definite period, the curve may, instead of the \ form, 
assume the shape of a \. 
The latter has also come to light in investigations published the 
other day by MADsEN & Nyman, *) which differed from mine in so 
1) Biochem. | Zeitschrift, Bnd. XI, Hft. 1—3, Festband Dr. H. J. HAMBURGER 
gewidmet. 
® Z.f. Hyg. u. Inf. Kr. Bnd. LVI, 
