64 IN RABBITS 



4. Pleuritis (usually with pericarditis) and peritonitis. 



5. Local lesion only. 



In the septicaemia, death ensues within eighteen to twenty- 

 four hours. The local lesion produced at the seat of inocula- 

 tion is slight. Bacteria are abundant in the parenchyma 

 (blood vessels) of the various organs. In the form character- 

 ized by peritonitis death ensues in three to seven days. The 

 local lesion, which in all these forms of disease increases in ex- 

 tent with the prolongation of the life of the animal, is here 

 characterized b}' more or less suppurative infiltration of the 

 skin and the subcutis. The peritonitis in its earlier stages is 

 characterized by punctiform hemorrhages on the caecum and 

 a fibrinous or cellular exudate. It always contains immense 

 numbers of bacteria. When pleuritis is also present the exu- 

 date usually involves the pericardium as well. It varies in 

 amount according to the duration of the disease and is essen- 

 tially the same as the peritoneal exudate. 



The form characterized by pleuritis and pericarditis with- 

 out peritonitis is interesting in so far as the seat of inoculation 

 does not explain the localization, for, in every case, the inocu- 

 lation was made in the region of the abdomen. The lungs 

 may become hepatized secondarily through invasion from the 

 pleura if the animal lives long enough. 



Lastly, the form of disease in which the only localization 

 is a ver3' extensive suppurative infiltration associated with 

 hemorrhage and oedema of the subcutaneous tissue is not 

 common. 



It should be stated that the cultures from the same out- 

 break continued to produce the same form of disease in rabbits 

 until modified by age. The maintenance of a certain uniform 

 virulence for j'ears is well exemplified by a variet}' isolated 

 in the summer of 1890. This variety was fatal to rabbits 

 within twenty hours when first isolated, and this degree of 

 virulence has maintained itself up to the present, a period of 

 nearly four years." 



§ 54. Modifications of the septicaemia type by in- 

 creasing the resistance of rabbits. By the infection of steril- 

 ized cultures which increase the resistance of rabbits, Smith and 



