274 
ZOOLOGY: R. W. GLASER 
Proc. N. a. S. 
teria concerned and incubated for five days. After this time the cultures 
were tested for the presence of nitrites by the use of the sulphuric acid, 
potassium iodide, starch reaction and the naphthylamine, sulphanilic 
acid, acetic acid test. Of course, the absence of nitrites may not indicate 
non -reduction of nitrates, since the nitrites formed prior to the test may 
have been reduced to free nitrogen or ammonia. Nevertheless, in that 
case a nitrate reaction should not be obtained. The presence or absence 
of nitrates after five days growth was tested in each case by evaporating 
the culture to dryness and by adding phenolsulphonic acid, diluting with 
water and transferring to a Nessler jar. Sodium hydroxide solution was 
added to make it alkaline and the color reactions compared. 
The table shows that each species capable of reduction has a distinct 
range. Bacillus prodigiosus has a greater range than Spirillum Metch- 
nikovi, but the latter has the power of reducing nitrates in a weaker con- 
centration. Prodigiosus', on the other hand, has the power of reduction 
in greater concentrations of the salts. This inability of Metchnikovi to 
reduce in greater concentrations may be associated with the inhibiting 
influence of high osmotic pressure on growth, for it will be seen that Metch- 
nikovi grew weakly in concentrations greater than 0.1 mol. That growth 
and ability to reduce are not always associated, however, can be seen in 
the case of B. coli communis which grew poorly in 0.5 mol. concentration 
and reduced NaNOs. 
A distinct range of reduction power in various concentrations can also 
be noted for some of the other species. Some have a smaller, some a greater 
range. In so far as the reducing power is concerned no difference was 
noted between sodium and potassium ions. Nevertheless, a slight differ- 
ence between sodium and potassium ions in the amount of growth was 
observed. In 4 mol. NaNOs Coccobacillus acridiorum variety "Souche 
Cham" grcvv poorly, but no growth whatever was obtained in the same 
• concentration of KNO^. The same condition was observed when the An- 
thrax bacillus was used. This difference in ions was further observed by 
using B. coli communis, where the sodium salt gave a* poor growth at 0.5 
mol. concentration and the potassium salt a good growth at the same con- 
centration. The difference between ions and growth is not dependent 
upon variations in the number of bacteria originally introduced into the 
cultures for the amounts were previously carefully calibrated. 
^ Contribution from the U. S. Bureau of Entomology in cooperation with the Bussey 
Institution of Harvard University. (Bussey Institution, No. 173.) 
