128 
IOWA ACADEMY OF SCIENCES. 
Per cents. 
Solution. 
A 
B 
C 
D 
E 
Asparagin 
0.2 
0.2 
0.2 
0.1 
1.0 
Mp-SO. 
.1 
.2 
.1 
.1 
KaHP 04 
.1 
.1 
.1 
.1 
Crlycerin 
2.0 
Solution B. had a tinge of color and quite a growth. 
Solution C. had color, but little growth. 
Solution D. had very little color, made little growth. 
Solution E. had good growth but no color. 
In solution B the magnesium sulphate was eliminated to 
see if it would make a change in the amount of pigment. 
A faint suspicion of color and same growth as in solution 
A was noted. In solution C potassium phosphate was 
eliminated with the result that the color was about like 
that in A, but the growth was poor. Then to see if it could 
be the organic matter that was necessary, the asparagin 
was reduced to one tenth of one per cent with the result 
of but slight growth and no color. In solution E, glycerin 
was added and the result was a good growth but no color. 
Kuntze and Nuesske hold that magnesium sulphate is 
necessary for color, and potassium sulphate for bacterial 
growth. By the above experiments the deduction would 
seem to hold good for B. vioalceus. 
Three other solutions which contained each one-tenth 
of one per cent of the three sugars were prepared. Growth 
and color seemed to be stopped in the solutions that con- 
tained dextrose and saccharose. It must be remembered, 
however, that the organism had been kept for five months 
in a saccharose bouillon solution. 
In the lactose solution the growth was vigorous but 
without color. The other sugars semed to be sufficient in 
amount to inhibit all growth if not to kill the organism 
outright. Dr. F. E. Hellstrom experimented on the 
effect of small quantities of glucose on the vitality of bac- 
teria and found ‘That the addition of glucose in the pro- 
portion of 0.1 per cent for cholera, 0.2 per cent for typhoid, 
and 0.3 per cent for other kinds of bacteria to simple 
