270 OEIENTAL PLAGUE chap. 



pigs inoculated cutaneously with plague material (by an 

 abrasion or a scratch of the cutis) develop, as a general 

 rule (unless, indeed, the infective material be of extreme 

 virulence), plague in what I have termed the " subacute 

 form " ; a form marked by necrotic bubo, necrotic nodules 

 in the spleen and liver, and particularly by necrotic 

 nodules and necrotic patches in the lungs. In these cases 

 death occurs generally in from four to seven or nine days 

 (rarely earlier than four or later than nine days), provided 

 the infecting material be of a moderate degree of virulence, 

 such, for instance, as on subcutaneous injection causes 

 death in three to four days, without the above necrotic 

 changes. 1 



Examining sections of the organs containing the 

 necrotic nodules and necrotic patches of guinea-pigs dead 

 of subacute plague, it is seen that while the central parts 

 of the necrotic nodules are crowded with B. pestis, the 

 peripheral portions (except their vessels), although quite 

 broken down into dead debris, contain few, if any, bacilli. 

 From this it may be inferred that, as is the case in other 

 bacterial diseases associated with necrotic changes of the 

 tissues, such necrosis is not caused by the mere presence 

 of the bacilli themselves, but by the toxin produced by 

 them. As an illustration may be mentioned the necrotic 

 action of the diphtheria toxin on a mucous membrane. 



In view of the above two considerations, I determined 

 to inject into a series of animals the dried organs (contain- 

 ing organ-toxin and dead bacilli) of various rodents dead 

 of plague, with the purpose of ascertaining the ability 



1 As I have on a former page pointed out, there exists in respect of cutaneous 

 inoculation a marked difference of reaction between the guinea-pig and the rat ; 

 in the latter animal cutaneous inoculation is the most reliable way of causing acute 

 plague with fatal issue in two to three days. 



