INFECTION AND IMMUNITY. 563 



cerned in the production of the so-called " hemorrhagic 

 septicaemias." When running their normal course the 

 vpecific organisms of these diseases cause typical septi- 

 caemias in susceptible animals ; but often, from causes not 

 entirely clear, the animals die with only local lesions, or 

 with but very few organisms in the internal viscera. We 

 see here conditions analogous to those observed in the 

 two experiments with anthrax, viz., we find a group of 

 diseases that are properly classed as septicaemias, be- 

 cause of the usual general invasion of the body by the 

 organisms concerned in their production, but which 

 frequently assume a purely local character in both 

 instances proving fatal to the animal infected. From 

 what we have seen it is manifestly probable that, 

 whether these diseases be designated as septicaemias or 

 as toxaemias, death is produced in all instances by 

 poisonous substances that are generated by the infecting 

 bacteria. In the case of typical anthrax, and other 

 varieties of septicaemia, the production of this poison 

 is associated with the general dissemination of the 

 organisms throughout the body ; while in those infec- 

 tions often referred to as toxaemias, of which diphtheria 

 may be taken as a type, the poison is produced by the 

 organisms that remain localized at the site of invasion, 

 and is thence disseminated throughout the body by the 

 circulating fluids. Infection thus far, then, appears to 

 be a chemical process. 



In still another group of infections there is neither 

 a general distribution of the organisms throughout the 

 vascular system nor an elaboration of toxins that can 

 be readily separated from the organisms manufactur- 

 ing them. In these infections, of which typhoid fever 

 and Asiatic cholera may be taken as conspicuous ex- 



