346 BACTERIA IN RELATION TO PLANT DISEASES. 
This organism does not produce acids in milk, but there is a slowly increasing alka- 
linity, and after some days (3 to 10 or more) the casein is precipitated as a finely divided, 
voluminous, mobile mass, which settles slowly. These phenomena are best observed in 
litmus-milk. The litmus in such cultures is slowly reduced, but on the death of the organism 
it is oxydized back into a deep blue. In the end the casein is partially peptonized, but this 
change does not occur rapidly. The organism makes a good growth in milk and forms a 
bright yellow rim (plate 20, figs. 2-4), and sometimes a pellicle. In old cultures sheaf- 
like crystals of tyrosin occur. 
In April, 1898, two 10 cc. tubes of milk, which had received 4 steamings and been under 
observation for a month unchanged, received 200 mgs. each of thymol. One was put away 
as a check, the other received 8 cc. of whey from a milk-culture of Bact. hyacinthi 33 days 
old, after this had been heated in the water bath for 10 minutes at 51.8° C. (4° above the 
thermal death point). There was no change in the check tube. In the other, there was 
copious precipitation of the casein in 48 hours, but no evidence of bacterial growth either 
then or subsequently (11 days). In October, 1898, the experiment was repeated with the 
same result. In this experiment (fig. 143) 10 cc. of sterile milk received 3 cc. of whey from 
a milk-culture 10 days old. One hour after 
adding the whey the tube was heated for 20 
minutes at 52°C. in the water bath to destroy 
the bacteria. In 24 hours the milk was entirely 
coagulated. A small drop from this tube was 
now transferred to bouillon but did not cloud 
it (5 days). At the same time another tube of 
the same milk received 3 cc. of whey from an- 
other milk-culture of the same organism, the 
only difference being that in this case the milk 
was heated for 10 minutes at 80°C. after adding 
thewhey: This, to destroy the supposed enzyme. 
Result: No change in the milk (7 days). 
These experiments indicate the presence of a 
lab ferment. 
In litmus-milk (and in bouillon) contain- 
ing ethyl alcohol, a volatile acid is formed, and 
there is a fragrant odor in the steam. Methyl 
alcohol is not decomposed. 
There is a moderate, smooth, wet-looking 
growth on steamed potatoes standing in dis- 
Fig. 143.* tilled water, but it is not prolonged or copious. 
the color on potato is at first wax-yellow, but 
after some time it is dulled to a brownish yellow. At 20°C. to 25°C. the streak is not visible 
until the second or third day when inoculations are made from fluids. Growth on potato- 
cylinders is much increased by the addition of a little cane-sugar, dextrin, or malt-diastase. 
The action of the organism on starch is feeble, and the water surrounding the potato is 
never converted into a solid mass of slime as in case of Bact. phaseoli, Bact. campestre, Bact. 
juglandis and other starch-destroying organisms. On potato cylinders first soaked in pure 
water to remove the slight amount of sugar and acids on the cut surface and then tubed, 
growth did not occur or was delayed and scanty. Young cultures have no smell; in old 
cultures there is a feeble odor. Type of growth on potato like Bact. stewarti (P1. 17, fig. 2). 
*Fic. 143.—Two tubes of sterile milk to which was added equal volumes of whey from old cultures of Bact. 
hyacinthi in milk. Whey added to tube b after heating to 80° C. (to destroy enzyme); whey added to tube a after 
heating to 52° C. (sufficient to destroy bacteria only). Result: Milk curdled promptly in tube aand remained unchanged 
in the other. Oct. 1898. 
