110 INFECTION 



Aside from bacterial toxins, characteristic poisons are also produced 

 by certain of the higher plants (phytotoxins) and animals (zootoxins), 

 and although few are of medical interest, their study has thrown con- 

 siderable light on the phenomena of toxin-antitoxin immunity. 



Extracellular Bacterial Toxins. Definition. Bacterial toxins may be 

 defined as poisonous products produced by bacteria in both living tissues and 

 artificial culture-media. The symptoms resulting from their activity appear 

 after a certain period of incubation, and all are capable of stimulating 

 the production of specific antitoxins. They represent the chief poison- 

 ous product of bacteria, and are mainly responsible for the symptoms 

 of infection caused by the specific bacteria that have produced them. 



The true toxins causing infection in man are chiefly: 



1. Diphtheria toxin. 



2. Tetanus toxin. 



3. Botulism toxin (a form of meat poisoning). 



4. Dysentery toxin (Kruse-Shiga). 



5. Staphylolysin, streptolysin, and other bacterial toxins. 

 General Properties of Soluble Toxins. Many of the true toxins are 



extremely labile, and susceptible to the action of heat, light, age, etc.; 

 consequently an absolutely pure toxin is practically unknown. Oxygen, 

 even as it occurs in the air, is harmful; all oxidizing agents, including 

 the oxidizing enzymes, quickly destroy them, and Pitini 1 has ascribed 

 the harmful effects of toxins to their power of reducing the oxidizing 

 capacity of the tissues. Some substances seem to attack only the 

 toxophore portion of the toxin molecule, e. g., iodin and carbon disulphid 

 (Ehrlich). In the preparation of antitoxin, the first doses of toxin are 

 frequently modified by adding a chemical of this nature. According 

 to Gerhartz 2 z-rays tend to weaken the toxins. 



Because of their great lability, the toxins do not lend themselves to 

 accurate chemical analysis. Our knowledge of them has been gained 

 largely through a study of the lesions and symptoms produced by in- 

 jecting the toxins into susceptible animals. 



They are, so far as known, uncrystallizable and thereby differ from 

 ptomains; they are soluble in water and dialyzable through thin but not 

 thick membranes. They are precipitated along with peptones by 

 alcohol, and also by ammonium sulphate. 



The toxins are all poisonous, but in order to exert their toxic effect 

 they must enter into chemical combination with cells; hence there is a 

 necessary period of incubation before symptoms of their activity appear. 

 1 Biochem. Zeit., 1910, 25, 257. 2 Berl. klin. Woch., 1909, 46, 1800. 



