PATHOGENIC OR NON-PATHOGENIC TO ANIMALS? 89 
harbored by plants. Of those known to cause animal diseases none have ever 
been found naturally present in plants, but some of them, such as the typhoid 
bacillus, the anthrax organism, etc., have been shown to live for a number of 
days or weeks when injected into various living plants, and in some instances have 
been found to multiply a little in the vicinity of the wounds. In general, their life 
is short in such situations, they do not penetrate far into the tissues, and they are 
manifestly on the defensive. If they 
can do no better when injected into 
vegetable tissues in enormous quanti- 
ties, it seems rather unlikely that under 
ordinary natural conditions they would 
find their way into plants so as to 
make them dangerous for food. In 
this connection the reader is referred 
to Volume II, where this subject is 
\ ' ' discussed more fully. More danger is 
likely to result from pathogenic organ- 
isms carried on the surface of plants, 
| a especially on salads and fruits which 
eS = are not cooked. In times of the gen- 
| EA ee eral prevalence of typhoid fever, chol- 
| rie bese : era, ot the bubonic plague, the writer 
; for one would certainly prefer to forego 
4 salads and to eat only freshly cooked 
vegetables. The danger from such 
foods in time of epidemics is very 
great, especially in localities where 
ditch-water is frequently sprinkled on 
the vegetables to freshen them, e. g., 
in parts of southern Italy. 
Most saprophytes when injected 
into living plants behave in the same 
way as the animal parasites, z. e., they 
either die at once or maintain a pre- 
carious existence for some weeks in the vicinity of the wound and then. succumb. 
The writer has made many experiments, with negative results. The most extensive 
published series of experiments are those of Zinsser (Jahrb. f. wiss. Bot., 1897). 
To get a particular disease, the parasite must be used and not some other organism. 
This the writer has observed over and over again. his statement holds good with 
plants the same as with animals. In case, however, of the less typical plant diseases 
(soft rots) various members of a group of closely related organisms may produce 
essentially similar phenomena. ‘This is paralleled, however, in certain of the less 
typical animal diseases. 
Pg. 73:* 
*Fic, 73.—Seedling sweet-corn plant extruding water from its leaf-tips. Most of the infections 
by Bacterium Stewarti take place during this stage of growth, the bacteria passing down the leaf 
through its vessels and entering the stem through the lower nodes. Natural size. 
