Acute Fibrinous Pneumonia. Pneumonitis in the Horse. 255 



Pneumonia from Contusion of the chest, fracture of a rib, or 

 puncture or laceration of the lung is recognized. 



Contagion. The presence of a contagium 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 

 escapes, 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, cow-pox, appear locally before any constitutional dis- 

 turbance occurs, which comes on later as the result of extensive 

 local disease and the circulation of toxins in the blood. It places 

 contagious 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 

 animals. It must also be allowed that the same germ does not 

 always 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 

 temporarily non-virulent or only slightly virulent, and remain 

 pathologically quiescent, as for example during the summer 

 months, to reassert themselves later when the conditions become 

 more favorable to pathogenesis. 



