igog| LIPMAN—EFFECTS OF SALTS ON BACILLUS 107 
material and is homogeneous in character. Of this homogeneous 
liquid 1°° was drawn off with a sterile pipette for inoculation into 
each flask to be tested, the greatest caution being used to prevent any 
particle of membrane from entering the pipette as the liquid was 
drawn up. This was the most satisfactory method of inoculation of 
several tested and yields concordant results in the duplicate series. 
All the solutions employed were made practically neutral. The 
‘incubation was carried out in a thermostat at a temperature which 
varied between 28° and 29°C. The incubation period was two days in 
the case of the single salt solutions, and two and one-half days for the 
binary solutions. The amount of ammonia formed, which was used 
as a criterion for establishing the efficiency of B. subtilis in the various 
solutions, was determined as follows: At the end of the incubation 
period the culture solutions were transferred to flat-bottomed Jena 
distillation flasks, diluted to 300-350°°, an excess of magnesium oxid 
added, and distilled. The amount of ammonia in the distillate was 
titrated against standard acid, cochineal being used as the indicator. 
Sterile blanks were run on all determinations, each of which was made 
in duplicate, and the tables given below represent averages of at least 
three sets of such duplicates and in some instances of five and six sets 
of duplicates. 
Experiments with single salts 
In determining the salts to be tested the writer was guided by the 
alkali and alkaline earth constituents-of soils. ‘The sodium, potas- 
sium, calcium, and magnesium salts are important factors in plant 
nutrition and are always present in soils; in some cases, indeed, one 
or more of them may be present in such excess as to inhibit plant 
growth materially and in some instances completely. Such soils we 
find in California and other states under the common appellation of 
_ “alkali lands.” It was decided, therefore, to test the salts of the 
alkalies and alkaline earths above mentioned, to determine the 
degree of toxicity of each for the bacteria experimented upon. Since 
from similar work on animals and plants, the anion of salts was 
found to have comparatively little effect, a chlorid of each metal was 
_ €mployed for the sake of uniformity. 
