IOWA ACADEMY OF SCIENCES. 
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bouillon (2 liters of water to 1 kg. meat), without peptone, 
and with a neutral or faintly acid initial reaction, exerts 
within a few days a deleterious action, owing to the 
medium turning acid. When the medium contains a still 
smaller quantity of nutritive material, a less amount of 
glucose suffices to bring about a fatal effect; and con- 
versely, when the amount of nutritive substance is greater, 
a larger amount of glucose is required to exert a pernicious 
action. A small quantity of glucose in bouillon is favor- 
able to the increase of essential aerobes, and thus the 
amount of glucose stands in direct relation to that of the 
nutritive material in the bouillon.” 
Koosowicz, the bacteriologist, cultivated B. prodigiosus 
in solution containing: 
0.3 per cent solution of saccharose 
.25 per cent solution of KH 2 PO 4 
.005 per cent solution of Ca^ (P 04)2 
.25 per cent solution of MgS 04 
.25 per cent solution of (NH 4 ) 2 HPO 4 . 
.2 per cent solution of NH 4 CI 
The organism produced a citrine yellow coloring 
material which diffused through the medium. The yellow 
coloring usually appears in the course of two or three 
weeks, transferring same to potato or meat bouillon gave 
red colonies. Ked colonies were produced by B. lacto- 
ruhefaciens and M. agilis. B. xynantheum also produces a 
reddish-brown color which is intensified in media con- 
taining MgS 04 . 
Migula says that B. prodigiosus produces red color 
in acid medium. In neutral, it is colorless. Colorless col- 
onies also occur from exposure to light. B. kiliensis pro- 
duces on potato at first a brick red color, later red, and on 
neutral agar, yellow red. B. cyanogenus produces blue 
color only in acid medium. In alkaline medium a dirty 
gray fluorescence, on potatoes a yellow. 
Thomas Milburn made an exhaustive study of the influ- 
ence of grape sugar on B. prodigiosus. He made up various 
solutions, containing different per cents of glucose. 
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