126 
IOWA ACADEMY OF SCIENCES. 
In order to test for gas production a fermentation 
tube which contained bouillon was inoculated in 
May, 1904. This was kept during the summer. In 
September a thick growth in the bottom of the neck of the 
tube and a tough leathery layer was on top of the liquid. 
It was, without doubt, a pure culture. Inoculations were 
made on the usual cultural media. Growth in many cases 
appeared, but no color could be obtained on agar, gelatine, 
potato, or blood serum. To test for involution forms, it 
was grown in a standard asparagin solution. They were 
easily found and a slight color first appeared on the edge 
of the medium. It later was dissolved. The organism had 
been grown for a long time in sugar bouillon and evidently 
it had lost its power to make pigment. However, it must 
be noted that the media had been made for regular labora- 
tory exercises and had been prepared with special pains to 
keep it free from nitrogen. The results from these last 
inoculations were as follows: 
Agar Stah.—lAo growth along stab but a white glisten- 
ing growth on top. No color. 
Agar Slant . — Abundant growth of glistening white viscid 
colonies. No color. 
Potoio.— Granular shiny colonies. Brownish. 
In order to get a solid medium of known composition a 
paste of rice flour was made and another of arrowroot 
starch. These were partially cooked and then put into 
tubes and sterilized for twenty minutes in an autoclave. 
The tubes were then inoculated from the sugar bouillon 
culture that had been growing all summer. The results 
were as follows: 
Arrowroot . — In twelve hours a spot of purple color could 
be seen. At the end of a week it had penetrated through 
the medium. At the end of a month the paste was colored 
throughout and was half liquefied. Here then was the 
proper nutrient medium. The arrowroot is pure starch 
and the B. violaceiis var. must produce an enzyme that 
reduces the starch. 
