164 



MANUAL OF POISONOUS PIvANTS 



when taken into the body of man or animal. In fact, such decomposition pro- 

 ducts are known and as most of them, probably all, are basic, containing nitro- 

 gen, they have been grouped with that general class of vegetable alkaloidal sub- 

 stances called Ptomains. If other poisonous substances than Ptomains are 

 developed , they are not known at the present time. In addition to these poison- 

 ous substances that arise as decomposition, other poisonous substances are pro- 

 duced by certain bacteria which are strictly synthetic, that is not produced 

 by the breaking down of complex compounds into more complex forms. The 

 exact chemical nature of these substances is not understood, the reasons for this 

 being that they are extremely unstable, it being impossible to heat them 

 without destroying, and they cannot be recognized by any known chemical 

 means. They must be distinguished and differentiated, and often detected only 

 by animal inoculation and experimentation. These soluble substances excreted 

 by the bacteria are called toxins. The term toxin is rather an unfortunate choice, 

 because it refers simply to their poisonous properties. In the broad sense, any 

 poisonous substance is a toxin, but in the sense in which it will be here used, 

 toxin indicates specific bacterial poisons excreted into the medium in which the 



^ *® 



I* 



Fig. 23. Bacillus cloaceae 

 from corn, cause of corn 

 disease, also found in sewage. 

 Supposed at one time to pro- 

 duce toxic substances to which 

 was attributed the corn stalk 

 disease. After Burrill. 



I ?'^' l^- , ^°?''"'"T?"sh.t (.Bacillus Sorghi). b Young plant infected with the organism. 

 o leaf and sheath, c Bacilli. Modified after Kellerman and Swingle. 



organism is growing, and producing upon inoculation, anti-toxins. In addition 

 to the products above mentioned, many bacteria undoubtedly owe their pois- 

 onous or intoxicating qualities to the fact that the protoplasm of living matter 

 of the organism is poisonous or contains poisonous substances which are not 

 excreted into the surrounding medium. When bacteria of this type are allowed 

 to grow in favorable culture media for a considerable length of time, there is 

 a certain amount of self-digestion or autolysis which takes place and these 



