BACTERIAL POISONS. 189 



mal may remain alive for days afterward. In some respects 

 the toxins resemble the physiological ferments, ptyaline, pepsin, 

 and the like; but they differ from these in that the physio- 

 logical ferments are not themselves used up in the process of 

 fermentation, whereas the toxins are used up in the production 

 of disease. After starch has been converted into sugar by 

 ptyaline, the ptyaline may be recovered and used over and over 

 again to convert more starch; but after tetanus, toxin has pro- 

 duced tetanus in an animal it cannot be recovered, since it has 

 become firmly united to the cells. Toxins, therefore, are very 

 peculiar bodies, behaving like ferments in requiring consider- 

 able time to produce effects, and acting like unorganized poi- 

 sons in being used up in the tissue changes which they produce. 

 Certain substances derived from the vegetable kingdom behave 

 in the same manner as bacterial toxins; ricin, abrin and robin 

 are examples of these. The poisons of scorpions and snakes 

 are also poisons which act like toxins. Other properties of 

 toxins will be considered in connection with antitoxin. 



Although, as has been stated/ the toxins have not been 

 isolated in a pure condition, they have, nevertheless, been ob- 

 tained in some cases in an extremely concentrated form. 

 Brieger and Cohn obtained a toxin from tetanus bacilli of 

 which o.ooopoop5 gram killed a mouse weighing 15 grams. 

 Roux and Yersin obtained a toxin from diphtheria bacilli of 

 which 0.00005 g ram was capable of killing a guinea-pig. These 

 figures indicate the extremely poisonous character of these 

 toxins. Such properties permit bacteria growing in a compara- 

 tively limited area to act upon parts of the body remote from 

 the focus of infection. 



A curious and unexplained effect of some toxins is the production of minute 

 areas of necrosis in certain viscera, as the liver. Such "focal necroses" have 

 been observed to be formed by the poisons of the baiclli of diphtheria, of typhoid 

 fever, and of the Micrococcus lanceolatus of pneumonia, and following the injec- 

 tion of abrin and ricin. 



Besides the extracellular toxins produced by the bacilli of diphtheria and 



