SIMILARITY BETWEEN TOXINS AND FERMENTS 245 



1. Both toxins and ferments are products of the metabolism of living 

 animal and vegetable cells, and may be extracellular (free enzymes and 

 soluble toxins) or intracellular (intracellular enzymes and endotoxins). 



2. Both exhibit a latent period before manifesting their individual 

 activities; in general, the effect of each is more rapid the larger the 

 amount present. 



3. Both substances represent a method or means by which the or- 

 ganism attempts to modify its environment and render the surroundings 

 suitable for its nutrition and growth. 



4. Both show a strong affinity for their substratum, and first manifest 

 their activity by combining with it. For example, fibrin placed in 

 gastric juice at C. and then repeatedly washed in cold water to remove 

 all traces of pepsin will undergo digestion when raised to body tempera- 

 ture. Similarly, if red corpuscles are placed in fresh tetanus toxin at 

 C. for an hour, washed repeatedly with cold normal saline solution, 

 and then raised to 37 C., hemolysis will take place, indicating the pri- 

 mary union of the bacterial hemolysin or tetanolysin with the corpuscles. 

 In a similar manner toxins probably unite chemically with tissue-cells, 

 as the toxin quickly disappears from the blood following its injection 

 and but a small fraction can be recovered from the excretions. Further- 

 more, the injection of an emulsion of these cells into other animals may 

 be followed by specific symptoms of intoxication. 



5. The activities of both toxins and ferments seem to depend largely 

 upon the temperature to which they are exposed. For instance, in the 

 example previously cited, tetanus toxin is harmless for the frog until 

 the temperature of the animal is raised to about 37 C. 



6. Both are usually affected by temperatures above 70 C. 



7. The one great difference, however, between toxins and enzymes 

 is the greater activity of the latter, even very minute amounts of an 

 enzyme having the power to split up or decompose large quantities of 

 complex organic compounds. An enzyme attaches itself to a substance 

 and absorbs water; the molecule breaks down, the enzyme is liberated, 

 and then attacks another molecule, this process being repeated until 

 large amounts of fermentable substances have been attacked. When, 

 however, a toxin has united with a substance it loses its identity, and in 

 this manner it follows the law of multiple proportions. This has been 

 discussed as it relates to the soluble toxins of diphtheria and tetanus, 

 and is likewise easily demonstrable in the action of tetanolysin upon 

 erythrocytes of the rabbit. It is true that a toxin may become dissoci- 

 ated and attack another molecule, but this action is different from that 



