Jan, is, 1917 
Blackleg Disease of Potato 
109 
on each of three consecutive days. It gave a faint blue color on the addi¬ 
tion of iodin solution, showing the presence of a small amount of starch. 
In ordinary culture tubes the appearance produced by B. atrosepticus , 
B. solanisaprus , B . melanogenes , IIIA, SE, and IIP was absolutely iden¬ 
tical, except that the last named produced somewhat more turbidity with 
less cloudiness. The characters shown were essentially those recorded 
for beef bouillon except that the growth was somewhat more vigorous 
and clouding appeared more rapidly, with a greater tendency to produce 
a ring or pellicle on the surface. This latter was of a granular nature 
and was less easily broken up than was the case with the pellicle formed 
on beef bouillon. 
In fermentation tubes filled with potato broth there appeared a 
thorough, uniform clouding of *both bulb and closed arm in from 18 to 
24 hours, but no gas of any kind was formed. 
With the cultures received as B . phytophthorus from Appel and as B. 
phytophthorus from Schuster the growth in ordinary culture tubes was 
the same as in beef bouillon except that with them it was also some¬ 
what more vigorous. In fermentation tubes containing the potato 
broth B. phytophthorus from Appel showed a marked contrast in the 
appearance of the same organism in fermentation tubes of ordinary 
beef bouillon containing carbohydrates. With the latter it was never 
observed to produce any visible clouding of the closed arm of the tube, 
while in the tubes of potato broth there was a faint clouding of the closed 
arm with a very perceptible growth on the third day. In the case of 
B. phytophthorus from Schuster the characters were not essentially dif¬ 
ferent from those observed with ordinary bouillon plus carbohydrates. 
There was a rapid and heavy clouding of the bulb, followed by a slow 
clouding of the closed arm. 
After the cultures had grown for 10 days, the broth was tested with 
iodin solution, but in no case did there seem to be any diminution of the 
amount of starch present. 
Miuk.—V ery little difference could be observed in the action of B. 
atrosepticus , B. solanisaprus , B. melanogenes, IIIA, SE, and IIP upon 
fresh skimmed milk sterilized by fractional steaming, except that SE 
produced a slow but evident digestion of the curd. With this excep¬ 
tion noted the record for the group when grown at a temperature of 
20 0 C. is: Coagulation somewhat delayed, not appearing for about 7 
days; extrusion of whey does not take place until the end of 10 to 14 
days, and only a slight amount is formed. Coagulum solid and appar¬ 
ently not digested, but readily breaks apart when probed with the needle, 
not slimy nor viscid, and when shaken forms nearly a solid mass with 
the whey. It will be noted that both Harrison (17) and Pethybridge 
and Murphy (26) report coagulation in 48 hours, but this is at 25 0 C. 
The latter gentlemen, however, recorded coagulation not appearing for 
five days at laboratory temperatures. 
