PRODUCTION OF TOXINS 115 



on several different kinds of cells, possibly indicates a mix- 

 ture of several toxins, or action on the same substance in the 

 cells. 



5. Toxins are very sensitive to the action of injurious 

 agencies such as heat, light, etc., and in about the same 

 measure that enzymes are, though as a rule they are some- 

 what more sensitive or "labile." 



6. Toxins apparently have maxima, optima, and minima 

 of temperature for their action, as shown by the destructive 

 effect of heat and by the fact that a frog injected with 

 tetanus toxin and kept at 20° shows no indication of poison, 

 but if the temperature is raised to 37,° symptoms of poisoning 

 are soon apparent. Cold, however, does not destroy a toxin. 



7. When properly introduced into the tissues of animals 

 they cause the body cells to form antitoxins (Chapter 

 XXVII) which are capable of preventing the action of the 

 toxin in question. 



8. The determining test for a toxin is its action on a living 

 cell. 



It is true that enzymes are toxic, as are also various 

 foreign proteins, when injected into an animal, but in much 

 larger doses than are toxins. 



A marked difference between enzymes and toxins is that 

 the former may bring about a very great chemical change 

 and still may be recovered from the mixture of substances 

 acted on and produced, while the toxin seems to be perma- 

 nently used up in its toxic action and cannot be so recovered. 

 Toxins seem very much like enzymes whose action is restricted 

 to living cells. 



Just as enzymes are probably produced by all kinds of 

 cells and not by bacteria alone, so toxins are produced 

 by other organisms. Among toxins which have been care- 

 fully studied are ricin, the poison of the castor oil plant 

 {Ricinus communis); abrin of the jequirity bean {Abru^ pre- 

 catorius); robin of the common locust (Robinia pseudacacia) ; 

 poisons of spiders, scorpions, bees, fish, snakes and sala- 

 manders. 



It has been stated that some enzymes are thrown out 

 from the cell and others are retained within the cell. The 



