Anatomical Changes. 137 



time some of the bacteria circulating in the blood become col- 

 onized in the bronchi and the pulmonary tissues and bronchitis 

 and pneumonia develop. In the meantime, the bacteria may 

 have disappeared entirely from the circulating- blood and re- 

 main only in the organs where pathologic changes are estab- 

 lished. Other bacteria, and also the l)acillus bipolaris, may 

 produce pneumonia without a preceding septicemia by gaining 

 access to the lungs either with the inhaled air or through the 

 blood-current. The localization of bacteria from the circulating 

 blood or their dissemination with the lymphatic current may 

 cause inflammation of the serous membranes of the thorax, par- 

 ticularly if the bacteria possess a higher degree of virulence. 

 Since diseased pulmonary tissue forms a good nutritive soil 

 for various bacteria, saprophytic microorganisms living in the 

 bronchi of otherwise healthy animals or in their neighborhood 

 may multiply rapidly (secondary infection) and produce fur- 

 ther changes. 



Anatomical Changes. These vary according to the several 

 microorganisms and their variable degree of virulence, also ac- 

 cording to the power of resistance of the affected animals and 

 to the duration of the disease. 



Aside from those cases which run their course as a pure 

 septicemia and which are not here considered, in its acute form 

 the disease not uncommonly presents the picture of a septic 

 pleuropneumonia. A serofibrinous exudate is found in one or 

 in both pleural cavities, the pleura being covered to an extent of 

 several millimeters with loose, juicy, fibrin membranes, which 

 are lusterless and studded with punctiform hemorrhages. The 

 lung is uniformly dense, void of air, friable in its anterior lower 

 portion ; frequently also to a greater extent, a reddish-gray 

 cloudy fluid may be scraped off the dark red-l)rown or grayish- 

 brown, finely granular cut surface. The interstitial connective 

 tissue appears uniformly serously infiltrated and forms yellow- 

 ish, gelatinous, reticulated stripes of varying width on a red- 

 brown or more grayish-brown background (marbled). Some- 

 times one sees lymph vessels with coagulated lymph and a 

 fibrinous exudate in the wider stripes (Lienaux). Of other 

 changes occasionally met with may be mentioned gelatinous in- 

 filtration in the neighborhood of the larynx and the pharynx, 

 hemorrhages into the tissue of the pericardium and peritoneum, 

 fibrinous pericarditis, acute swelling of the lymph glands, acute 

 gastro-intestinal catarrh, sometimes ulcers in the abomasum 

 (Beresow), cloudy swelling of parenchymatous organs, also, 

 according to Galtier, hemorrhages into, and fatty degeneration 

 of, the muscles of the rump, the extremities and of the heart. 

 The anatomical picture in sheep and goats is sometimes similar 

 to that of septic pleuropneumonia ; in young pigs, however, to 

 that of typical swine plague (see Vol. I). 



Very frequent findings in acute cases are bronchitis or ])ron- 



