128 CONDITIONS OF GROWTH. 
While many species grow in various media and under various 
conditions of temperature, etc., others are greatly restricted in this 
regard ; thus Bumm only succeeded in cultivating the gonococcus 
upon human blood serum, and even upon this was not able to 
‘ carry it through a series of successive cultures. It is very probable 
that certain species can only grow in association with others which 
elaborate products necessary for their development. 
Substances favorable for the growth of a particular species may 
restrain its development if present in too large an amount. Thus 
the phosphorescent bacilli multiply abundantly in a nutrient solution 
containing 2.5 per cent of sodium chloride ; but this amount would 
restrain the development of some other species, and a considerable 
increase in the quantity of salt prevents the growth of all microér- 
ganisms. In the same way the addition of two per cent of glucose 
to culture solutions is favorable for the development of certain spe- 
cies, and especially for the anaérobic bacteria ; but a concentrated 
solution of the same substance prevents the growth of all bacteria. 
The influence of one species upon the growth of another has 
been studied by various bacteriologists, and especially by Sirotinin 
and by Freudenreich. When several species are associated in the 
same culture one may take the precedence and the others may de- 
velop later ; or two or more species may develop at the same time ; 
or the growth of one species may prevent the development of an- 
other, either (a) by exhausting the pxbulum necessary for its growth 
or (0) by producing substances which inhibit the development of an- 
other species or destroy its vitality. 
Freudenreich found, as a result of his numerous’ experiments, 
that the following species cause a change in bouillon which renders 
it unfit for the growth of other species: Bacillus pyocyaneus, Bacil- 
lus cyanogenus, Bacterium phosphorescens, Bacillus prodigiosus, Spi- 
rillum cholere Asiatic. The following species do not cause such a 
change in bouillon as to render it unfit for the growth of other spe- 
cies : Bacillus typhi abdominalis, Bacillus anthracis, Bacillus septi- 
cemiz heemorrhagice, Spirillum tyrogenum. The following have a 
‘decided antagonism : Bacillus pyogenes foetidus prevents the growth 
of Spirillum cholere Asiaticee ; Micrococcus roseus prevents the 
growth of Micrococcus tetragenus. The cholera spirillum will not 
grow in sterilized cultures of Bacillus pyocyaneus, or in bouillon 
which has served for a previous culture of the same microérganism 
(Kitasato). Other bacteria which fail to grow in bouillon which 
has already served for the cultivation of the same species are Bacil- 
lus typhi abdominalis, Bacillus cyanogenus, Bacillus prodigiosus, 
Micrococcus roseus, etc. (Freudenreich). 
