Feb. 14, 1916 
Longevity of Soil Micro-organisms 
93 i 
would extend over a considerable period. Nestler (16) investigated an 
old herbarium and found that even after 23 years 90,000 colonies could 
be obtained from 1 gram of soil. Azotobacter (12) remain alive in 
soil samples if these samples are kept for 160 days in a desiccator 
and then 148 days in an air-tight condition. Germano's (9) results 
seemed to indicate that the organisms of typhoid fever and diphtheria 
did not live as long in soil as on fabrics, although the diphtheria bacillus 
averaged 20 to 40 days' longevity in all trials in soil. Firth and Horrocks 
(3) found that the typhoid bacillus would live for 23 days in dry sand. 
Pfuhl (18) found the typhoid bacillus to live 28 days in dry sand and 88 
days in moist garden earth. The bacillus of dysentery, on which he 
experimented at the same time, lived only 12 days in sand and 101 days 
in moist garden earth. Briscoe (1) found the tubercle bacillus to live 
213 days in garden soil. 
But little work has been done to determine the effect of different soil 
types on the longevity of organisms dried in them. The data offered in 
the literature on this point are not only scanty but far from recent. Mod¬ 
em texts hold that dust does not offer protection to many pathogenic 
organisms, the dangers due to ordinary dust being much exaggerated 
according to Rosenau (22, p. 72) and Chapin (3, p. 263). Dempster (5) 
found that the cholera vibrio lived only a short time in perfectly dry soil, 
but survived for a prolonged period in soil containing a small amount of 
moisture. The typhoid bacillus showed a greater tenacity of life in soil 
than did the cholera vibrio, but entire desiccation proved to be quickly fatal 
to it also. Comparison of the longevity of these organisms in white sand, 
gray sand, garden mold, and peat showed that with the exception of peat, 
which apparently contained substances toxic to the organisms, the nature 
of the soil did not have a direct influence on them. The vitality of the 
organisms appeared to depend rather on the moisture content of the soil 
than on its composition. Our experiments on the longevity of soil organ¬ 
isms in different types of soil have led to a modified conclusion. The 
longevity of vegetative cells in air-dry soil is probably, as Lipman (14, 
p. 228) suggests, due mainly to the presence of moisture in the hygro¬ 
scopic form, although undoubtedly the presence of organic colloidal sub¬ 
stances with a tendency to retain moisture and with other properties is 
of importance. Van Suchtelen, in speaking of the analysis of soil solu¬ 
tion as quoted by Giltner (10, p. 154), makes certain statements, which, 
on account of their immediate bearing on this subject, deserve direct 
quotation. He says: 
In many cases there was found in the soil solution a slime. This must be regarded 
as the first experimental proof of the presence of this substance in the soil, and it is not 
impossible that much of the irregular behavior of the life in soil can be explained to 
some extent with a knowledge of this slime. If I may be permitted, I should like to 
call your attention to the possibility of this substance having an effect on desiccation, 
diffusion, and other processes. 
