MORPHOLOGY AND BIOLOGY OF BACTERIA. 31 



minoid reactions. They are, however, in no less degree 

 toxic, so that there can be no doubt that they contain the 

 true specific poison. They are insoluble in distilled water, 

 but readily soluble in feebly alkaline water or water con- 

 taining sodium chlorid ; they are most readily destroyed 

 by acids, but, on the other hand, they are unaffected by 

 substances of a feebly alkaline reaction. For the details 

 of the preparation and of the properties of the toxins of 

 diphtheria and of tetanus reference may be made to the 

 proper chapters in the special section. 



To be separated from these toxins, formerly designated 

 toxalbumins, and which have, up to the present, been ob- 

 tained in a manner perfectly free from criticism only in the 

 two toxic-infectious diseases, diphtheria and tetanus, and 

 recently in botulism, are those poisons that are contained 

 within the bodies of the bacteria themselves. R. Pfeiffer 

 first obtained these from cholera-vibrios and typhoid- 

 bacilli, by destroying fresh agar smear-cultures through 

 the action of chloroform-vapor, or through exposure to a 

 temperature of 54 C. (129.2 F.) for an hour. These 

 poisons, in contrast with the virus of diphtheria and of teta- 

 nus, are not demonstrable in the filtered cultures. They are, 

 however, like the former, unstable in nature. Exposure 

 to temperatures above 60 C. (140 F.) markedly reduces, 

 without, however, completely abolishing, their activity. 

 According to Pfeififer's view, there remain secondary toxins 

 that prove to be much more stable, withstanding boiling 

 for several hours, but which are from ten to twenty times 

 less toxic. A still further important difference exists 

 between these intracellular poisons of typhoid fever and of 

 cholera and the toxins of the pure intoxication -diseases 

 diphtheria and tetanus ; while the former manifest their 

 activity in animals immediately after their introduction and at 

 once induce disease-symptoms, the latter only give rise to 

 their toxic manifestations after a well-defined period of in- 

 cubation. 



The physiologic properties of the poisons of typhoid fever 

 and of cholera will be thoroughly considered in the special 

 section. 



Finally, those toxic substances must yet be mentioned 

 that are known as bacterial proteins (Buchner). These differ 

 from the poisons already mentioned in withstanding a boil- 

 ing temperature, and they appear, in contrast with the 



