INFECTION 249 



discovered to suggest anything that is common to all, and 

 even if the tissues be examined microscopically such marked 

 divergencies are seen that we are still in doubt as to the 

 existence of a common factor. In the case of anthrax, a 

 true septicemia, the blood current is the seat of activity of 

 the exciting bacteria, and beyond congestion, enormous 

 numbers of bacteria in the bloodvessels and the escape of 

 serum into the tissues (edema), little else is to be seen to 

 account for death. On the other hand, in the case of miliary 

 tuberculosis, even though the involvement of the organs may 

 be general, there is no similar invasion of the blood stream. 

 The tubercles are circumscribed, are often surrounded by 

 healthy tissue and, though obviously distributed throughout 

 the body from a primary focus through the agency of the 

 circulating fluids, each tubercle may nevertheless be regarded 

 as a distinct local infection. There is, however, a conspicuous 

 difference between the lesions found here and those seen in 

 anthrax. The lesion of tuberculosis, the tubercle, is always 

 characterized by tissue death at and about its centre, i. e., 

 where the bacilli are located, even in the earliest stages of 

 its development. 



On postmortem examination of an animal dead of diph- 

 theria we observe conditions that are unlike those noted in 

 both anthrax and tuberculosis. There is neither an invasion 

 of the vascular system nor a distribution of conspicuous 

 pathological foci throughout the body. The bacteria are 

 confined to the primary site of invasion and when found in 

 distal organs are there only in small numbers and give no 

 evidence of an effect upon the tissues immediately surround- 

 ing them. 



Thus far, as a result of this review, we have two points 

 in common to the three distinct diseases, viz.: they are all 



