2i6 Veterinary Medicine. 



Contagion. The presence of a contagiiim in pneumonia is to- 

 day well established. Clinical observation had indicated this 

 even before the discovery of a specific germ, but recent bacterio- 

 logical investigations and the transmission of the disease by inoc- 

 ulation of artificial cultures have definitely settled the question. 

 It does not follow that all cases are contagious, nor equally so, but 

 the recognition of the contagious form satisfactorily explains the 

 prevalence of the disease in one stable while an adjoining one es- 

 capes, and the eruption of new cases in a stable after an animal 

 affected with the disease or convalescent from it has been intro- 

 duced. It has been objected that many horses stand in the stable 

 with pneumonia cases and escape, but so is it with glanders, cow- 

 pox, and many other affections. It merely argues an immunity 

 in the case of some, and for the disease germ a very limited 

 transmissibility through the air. The further objection that the 

 existence of lesions in the lung before the onset of fever, excludes 

 this from the list of infectious diseases, is untenable since many 

 undeniably contagious diseases, like cutaneous anthrax, glanders, 

 lung plague, cowpox, appear locall}' before any constitutional dis- 

 turbance occurs, which later as the result of extensive local dis- 

 ease and the circulation of toxins in the blood. It places conta- 

 gious pneumonia however in that long list of infectious diseases 

 which develop first locally in the seat of infection and later become 

 more or less generalized. 



It must be admitted however that the germ of pneumonia is 

 not the same for all cases of the disease and for all genera of ani- 

 mals. It must also be allowed that the same germ does not al- 

 ways maintain the same degree of virulence, and that it may even 

 live for a time on the buccal mucosa of an animal belonging to a 

 susceptible genus without any morbid result. In short we must 

 recognize that different germs of pneumonia may become tem- 

 porarily non-virulent or only slightly virulent, and remain patho- 

 logically quiescent, as for example during the summer months, 

 to reassert itself later when the conditions become more favorable 

 to its pathogenesis. 



BACTERIOIvOGY. 



a. Bacillus of Frikdla.nder. This is a short rod with 

 rounded ends, often merely oval, occurring in pairs, or chains of 



