716 
Journal of Agricultural Research 
Vol. V, No. 16 
with the development of the various synthetic culture solutions our 
knowledge of the nutritional requirements of micro-organisms has 
arisen (Pasteur, 1858, Raulin, 1869, Nageli, 1880). 
The gradual extension of the point of view of physiological response 
may be considered a guiding principle in cultivating organisms, and after 
a period of more or less accidental or random application of specific 
environments to influence growth or reproduction, a definite method 
based upon this teaching has been developed. Roux and Tinossier 
(1890), with the animal pathogen, Dematium albicans , secured marked 
reactions to specific environmental factors, especially nutrition and 
oxygen. At the same time Winogradsky (1891) began his well-known 
work with the nitrifying organisms which he isolated by his method of 
“ elective culture.” This method, which consists essentially of so estab¬ 
lishing the environment that only organisms of the desired type are able 
to develop, was carried to great perfection by Beijerinck (1901) with his 
similar “intensification” method. The bacteria and algae with which 
Beijerinck worked required or tolerated different amounts of free oxygen, 
different nutrition, especially mineral salts, and different temperatures. 
Beijerinck used these differences as a means of isolation of various forms 
from a complex substratum (Stockhausen, 1907). 
About the same time Klebs began his work on algae and fungi in pure 
culture. Where others were concerned with growth, Klebs (1896) 
made the pure culture answer unsolved questions of life history. He 
(1913) recognized in the organism definite potentialities—the heredity 
of the organism. The manifestations of these potentialities are seen 
in the reactions to environment and in the limits of the various factors 
tolerated. The particular line of development followed by the organism 
can be traced to conditions outside of the potentiality, either inner 
conditions inaugurated by the environmental complex or outer con¬ 
ditions which work through their ability to set up certain internal effects. 
From this line of reasoning it was but a step to the position that the 
development of an organism is the resultant of the environment working 
upon definite internal potentialities of the organism and that with a 
given potentiality the same external conditions call forth the same 
response with the constancy of a chemical reaction. This response 
may be predicted from the type of conditions given, and in this regard 
Klebs (1900) announced the following propositions, as based upon his 
work: 1 
1. Growth and reproduction are life processes, which among all organisms depend 
upon different conditions; among the lower organisms, probably external conditions 
determine whether growth or reproduction ensue. 
2. As long as the characteristic outer conditions for the growth of the lower organisms 
are present, reproduction does not set in* The favoring conditions for this process 
are always more or less unfavorable to growth. 
1 Author’s translation. 
