preciate the facility with which particles, large or small, 

 organized or unorganized, gain access to the circulation 

 through the lungs. 



Bacteria then, which, by virtue of their ubiquity, 

 are in constant and frequently recurring contact with 

 the animal body, are, like other minute bodies, organ- 

 ized and unorganized, frequently introduced into the 

 body through solutions of continuity of the integuments, 

 or through intact skin and mucous membranes, particu- 

 larly by way of the lungs. 



The burning question in pathology to-day is, in what 

 degree are the various species of bacteria, present in 

 human tissues during certain morbid conditions, to be re- 

 garded as the cause of the morbid processes with which 

 they are respectively associated ? Having already re- 

 viewed the conditions of eligibility for witnesses and of 

 authenticity for evidence, we are prepared to consider 

 in detail the present state of the question as to the indi- 

 vidual diseases. 



Before admitting the casual relation of a bacterium to 

 the disease, we must be convinced not only that all ob- 

 served phenomena can be easily reconciled with such 

 assumption, but also that they can be as plausibly ex- 

 plained by no other assumption. The evidence of such 

 causal relation must establish, therefore, i, the compe- 

 tence of the observer and the accuracy of the observa- 

 tion ; 2, the presence of a constant bacterial form in every 

 case of the disease, and in numbers sufficient to explain 

 the morbid phenomena ; 3, the demonstrable isolation of 

 the bacteria by successive cultures ; 4, the induction of 

 the disease in numerous healthy animals by inoculation 

 with the isolated organisms; 5, the reproduction of the 

 same bacterial form in the inoculated animal. Gauged by 

 this standard, the evidence already adduced warrants the 

 following unscientific but convenient classification : 



First. Disease, the demonstration of whose bacterial 

 origin has been completed, through inoculation with iso- 

 lated bacteria, by several competent observers anthrax. 



Second. Disease whose bacterial origin has been af 



