84 BACTERIOLOGY. 



Toxins. — It has been pointed out (p. 79) that a given 

 micro-organism produces a considerable number of chemical 

 compounds. It is possible for several of these products to 

 be more or less poisonous. In the case of the disease- 

 producing bacteria each one elaborates a highly toxic sub- 

 stance, which has been designated by the term toxin. It 

 is certain that these toxins, the specific bacterial poisons, 

 are made within the cell, by synthetic processes. Thus far, 

 no one has succeeded in isolating toxins in a strictly pure 

 condition, and consequently their chemical composition is 

 undetermined. While it is not known what the toxins are, it 

 nevertheless has been definitely shown that they are not basic 

 substances or ptomains, and that they are not proteins. 



Obviously the toxin of the diphtheria bacillus is differ- 

 ent from that of tetanus, or of cholera. Bach pathogenic 

 organism, therefore, makes a toxin which is characteristic 

 for that particular species. In the case of the tetanus and 

 diphtheria bacilli, the specific toxins readily pass out of 

 the cell into the surrounding liquid. Consequently, the 

 filtered cultures of such organisms may be intensely poison- 

 ous. It is possible, for instance, to obtain a filtered diph- 

 theria culture which will kill a guinea-pig in a dose of 

 0.002 c. c, or even less. The toxin, of course, makes up 

 probably only a small fraction of one per cent, of this dose. 

 The purified tetanus toxin was fatal to a 15 g. mouse in a 

 dose of 0.000,000,05 g. In other words, a mouse weighing 

 half an ounce is killed by Trsiinjir of a grain of the purified 

 toxin. The calculated fatal dose for a man weighing 155 

 pounds is djs grain. It is evident that these toxins are by 

 far the most powerful poisons known to man. 



In the instances cited, the specific toxin readily passes 

 out of the cell into the surrounding liquid. This, however, 

 is not always the case. As a matter of fact, the toxin is 

 usually retained within the cell and consequently such cul- 

 tures, when filtered, are but very slightly poisonous. The 

 toxin which is stored up within the organism may be 



