MORBID ANATOMY 



53 



be stated that the lungs and the digestive tract are the chief 

 seats of the disease, though other organs, notably the lymphatic 

 glands, are secondarily involved. The disease is localized in 

 the lungs and in the digestive tract most likely because the 

 bacteria gain entrance through the respiratory and digestive 

 passages. 



The lungs have been found dis- 

 eased in nearly every outbreak which 

 has been investigated. In some out- 

 breaks the lung lesions predominated 

 and pneumonia was the direct cause of 

 death. In individual cases, pneumonia 

 is absent but pleuritis and interlobular 

 oedema are genearlly present. In a 

 few instances interlobular emphysema 

 of the lungs has been observed. 

 With pneumonia the ventral lobes are 

 first attacked, then the cephalic and 

 azygos, and lastly the principal lobes. 

 This movement of the disease seems to 

 depend on gravity, inasmuch as the 

 diseased parts are marked off from the 

 healthy portion by a nearly horizontal 

 line. In other words, the most depend- 

 ent portions of the lungs are the ones ^""- *"■ ^"'^'^"- °f '^ 

 ^^ , _ , , ,• portion of luiiif shoTinntr in- 

 aftected nrst, and as the disease pro- r,, ,■ ,',, ■ , ', , 



' ^ fillralion into the interlobu- 



gresses upwards only a small portion la,- spaces with serum and 

 of the principal lobe directly under the lyviph. 

 back of the animal, remains pervious, provided the life of the 

 animal is maintained up to this point. In nearly all cases of 

 pneumonia in swine the disease invoh-es the regions described 

 which are indicated in the cut b}- shading. In exceptional 

 cases, where the disease is caused h\ lung worms or due to em- 

 bolism, the pneumonia in\'olves portions of the principal lobes 

 not contiguous to the ventral lobes. 



Two kinds of pneumonia are encountered, lobar and 

 catarrhal or broncho-pneumonia. In the former the vesicular 

 portion of the lung substance is chiefly affected ; in the latter 



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