CHAPTER XXI. 



THE HEMORRHAGIC SEPTICEMIA GROUP. 



THE Hemorrhagic Septicemia or Pasteurella Goup of bacilli com- 

 prises a number of organisms which possess in common peculiarities 

 of morphology, similarity of cultural characters and great patho- 

 genicity for animals. 



Morphologically they are short, ovoid bacilli of relatively large 

 diameter, measuring about 0.5 to 0.8 micron in the widest part, and 

 varying in length from 0.8 to 1.5 microns. The organisms usually 

 exhibit marked pleiomorphism in old lesions and in old cultures. 

 They are non-motile, uniformly Gram-negative, and exhibit a marked 

 tendency to bipolar staining; the stainable substance is collected at 

 the ends of the bacillus, separated by a central, faintly stainable area. 



The hemorrhagic septicemia bacilli grow well upon ordinary cul- 

 tural media, and they are chemically relatively inert. Indol is pro- 

 duced by certain types, but not by all. Gelatin is not liquefied. Acid, 

 but no gas, is formed in dextrose, lactose and many hexoses. The 

 fermentation of other sugars and starches has not been thoroughly 

 studied. 



The type of infection induced is usually an acute generalized 

 septicemia, which, because of punctate hemorrhages on serous sur- 

 faces, and in the internal organs, is called hemorrhagic septicemia. 

 Inflammation of the intestinal tract and frequently the respiratory 

 tract is usually an important feature of the infection. 



The most important animal diseases are chicken cholera, swine 

 plague, rabbit septicemia, and a similar disease of cattle and wild 

 herbivora. Plague is the disease of man which most closely approaches 

 hemorrhagic septicemia of the lower animals. 



The lesions caused by Bacillus pestis in experimental animals and 

 in the naturally occurring disease in rodents present many similarities 

 to the hemorrhagic septicemias, and occasionally a distinction must 

 be made between the plague bacillus and other members of the group. 

 The Indian Plague Commission state that Bacillus pestis may be 

 differentiated from the other members of the group by its ability to 

 develop and produce acid (but no gas) in dextrose and mannite media 



