32 Hemorrhagic Septicemia 



The bacteria wliicli through some cause become parasitic 

 lose in some of the cases their pathogenic character after leav- 

 ing the affected animal, and may change again to saprophytes. 

 In the majority of cases, however, after having become accus- 

 tomed to the organism of a certain animal, they attain an in- 

 creased virulence for animals of this particular species, and 

 therefore infect the animals more easily even without the 

 influences of predisposing causes. This relative virulence may 

 even increase for a time in the course of further generations, 

 or may become constant. More frequently, however, it dimin- 

 ishes again after a certain time. 



These characteristics of tlie bipolar bacteria explain the 

 variation which is observed in the appearance and spread of 

 the diseases belonging to this group. The common experience 

 with these diseases is that they appear periodically in certain 

 localities without any apparent connection to which the intro- 

 duction could be traced. In such cases the outbreaks can be 

 explained by a sudden increase in the virulence of the bacteria 

 which are present in the soil or in the healthy animal favored 

 by influences which reduce their resistance. Some of the infec- 

 tions develop through such conditions. In these the disease 

 does not, or only exceptionally, spread from animal to animal, 

 and it therefore remains sporadic, or at least confined to cer- 

 tain localities. In other cases although the disease appears 

 spontaneously the organisms which pass through the body of 

 the animals retain their pathogenic character for a long time, 

 thus spreading the disease by direct or indirect infection, and 

 disseminating the contagion to distant localities. Further, 

 among the diseases of this group there are some in which the 

 bacteria adapt themselves in the course of time to the animal 

 body to such an extent that as saprophytes they are no longer 

 capable of propagation, and therefore these diseases spread 

 almost exclusively by being introduced from outside or by 

 direct communication. 



The acquired or inherited virulence of the different varie- 

 ties of the bacteria is usually only manifested for certain species 

 of animals, so that a certain disease spreads usually only 

 among the animals of the same species. Exceptionally how- 

 ever, the infective agent may become dangerous for other 

 species. Thus frequently the infection of buffalo disease and 

 hemorrhagic septicemia of cattle causes in hogs symptoms re- 

 sembling swine plague. On the other hand, the virus of swine 

 plague sometimes produces a septicemic affection in sheep, 

 while feeding it to chickens causes a disease which corresponds 

 to fowl cholera. 



Ligrnieres succeederl in artificially producinpf a variety of forms of hemorrhagic 

 septicemia in different animals by injections of cultures of the bipolar bacillus of 

 different origin. Koske successfully infected different species of fowl per os with 

 swine plague bacteria. On the other hand, he failed in hogs to produce a disease 

 resembling swine plague with the fowl cholera organism. 



The ovoid bacteria may retain their virulence for months in the original 



