136 Report oF DEPARTMENT OF BACTERIOLOGY OF THE 
detailed discussion of the action of the enzym upon cell walls. 
In pursuance of the above plan, this is deferred and it must 
here suffice to state that the action consists in the softening 
and swelling of the walls and ultimately in the complete solu- 
tion of their middle lamellae in susceptible vegetable tissues, 
but that in all cases it stops short of complete solution of the 
cell membrane, a residue of cellulose always remaining. 
The studies here reported upon were carried on at various 
times during the years 1901-1904. The strain of the carrot- 
rot organism used has been the same throughout and is that 
isolated from decaying carrot tissues in 1899 and since car- 
ried in culture, practically all of the time in beef broth, at the 
ordinary laboratory temperature, 16°—22° C. 
The question has arisen as to whether during this time 
reduction has occurred in -pathogenicity and rate of enzym 
production. Van Hall (1903) found that his iris rot organ- 
isms lost pathogenicity to iris after only four weeks in labora- 
tory culture and his experience with these led him to expect 
this as a rule with such organisms. Laurent’s (1889) and 
Lepoutres’ (1902) experiments suggest a like probability. 
Potter (1900:445) found no such rapid loss of pathogenicity 
in his turnip rot organism. 
In the case of B. carotovorus there has, in our judgment, 
been a considerable decrease in pathogenicity since our first 
trials of 1899. The change has, however, been a gradual one 
rather than rapid or radical, and, therefore, difficult to esti- 
mate. The virulence and rate of invasion of tissues has always 
varied with vegetables and environmental conditions, but it 
is certainly less vigorous in attacking even the more suscep- 
tible plants now than it was in our earlier inoculation ex- 
periments. <A culture of ths organism was sent to Messrs. 
Harding and Stewart of the New York Experiment Station 
in 1902. They reported it actively pathogenic at first, 1902, 
but wrote us a year later that it had lost practically all 
pathogenicity. Meanwhile our own cultures had not changed 
in any such radical way. In ‘this connection it is worthy 
of remark that Harding and Stewart kept their cultures on 
agar whereas ours were carried in broth. B. carotovorus is 
