INFECTION AND IMMUNITY. 417 



that we have here a condition with which mechanical 

 plugging of the capillaries could have had nothing to 

 do, for there are no organisms in the blood to interfere 

 with its circulation. Our hypothesis then with regard to 

 the condition found in our first case of anthrax is again 

 not tenable. Similarly, if an animal that has died of 

 tetanus be examined, we do not find the bacilli in the 

 tissues and circulating fluids generally, and, indeed, 

 often fail to find them at the point of injury. Plainly, 

 these fatal results following upon inoculations with the 

 diphtheria and the tetanus bacillus, with their accom- 

 panying tissue changes, occur from the presence of a 

 something that cannot be detected by either cultural 

 or microscopic methods, and this something can be 

 only a soluble substance that is produced by the 

 growing bacteria at the site of inoculation, gains ac- 

 cess to the circulation, and through this channel causes 

 death, for it is hardly to be imagined that the insignifi- 

 cant wound made in the course of inoculation could 

 per se have had this effect. In other words, these latter 

 animals have died from what is called toxcemia (poison 

 in the blood), a condition conspicuously different from 

 septicaemia, as seen in our first animal dead of anthrax. 

 There are, again, other infectious diseases, many of 

 which are known to present variations from what might 

 be considered a typical course, that may still further 

 serve to support the view that infection is a process in 

 which the mechanical effect of organisms in the cir- 

 culating fluids is of little consequence. Conspicuous 

 among these are the infections that follow upon the in- 

 troduction into the tissues of susceptible animals of cul- 

 tures of the micrococcus lameolatus (pneumococcus), of 

 the bacillus of chicken cholera, and of the organisms con- 



