394 Contagious Pleuro-piieumonia. 



A commission (Commission Dumas), appointed in 1850 for the study of the 

 disease under the presidency of Bouley, found that out of 100 cattle 32 resisted 

 infection. According to Lutz on three premises in the County Bars (Hungary) out 

 of 246 Hungarian fattened steers four {1.6'6'/c) became affected, out of 174 fattened 

 steers of higher breeds 22 (17.32%), of 32 cows of the same breed 5 (15.63%), of 

 15 similarly bred young stock 9 (60%) were attacked by the disease, although all 

 animals were kept under the same conditions and were kept together in the stables. 



Pathogenesis. The virus wliich in all probability enters the 

 lungs with the inhaled air, appears to propagate first in the 

 Ij^nph spaces of the interlobular connective tissue, where it 

 causes an inflammatory process, as a result of which the spaces 

 become filled with serous exudate and therefore distended. 

 With this a serous inflammation of the surrounding connective 

 tissue soon becomes associated, and the inflammation spreads 

 to the neighboring lobules, which from tlieir periphery towards 

 the center become filled with a serous, cellular, later coagulating 

 exudate, containing also a few red blood corpuscles. The in- 

 flammation gradually involves an increasingly larger part of 

 the lungs, producing inflammatory infiltration of the alveoli, 

 while the exudate contained in the previously affected parts 

 of the alveoli undergoes fatty degeneration. The virus also 

 reaches the pleural tissue, as well as the connective tissue of the 

 mediastinum, and there produces serous infiltration, while acute 

 swelling occurs in the neighboring Ipnpli glands. 



As the inflammation extends to the h^nph spaces of the 

 walls of the vessels, it causes coagulation of the blood in parts 

 of these vessels, by which a smaller or larger part of the lungs 

 is excluded from the blood circulation, and therefore becomes 

 necrotic (ischemic necrosis). This affected part of the lungs 

 separates later from the still sufficiently nourished surround- 

 ings, and a connective tissue capsule forms around it, in the 

 cavity of which the necrotic piece of lung lies free as a so- 

 called sequestrum. 



The sequestration represents essentially a healing process, 

 and as a matter of fact when only a small part of the lung 

 becomes necrotic, it is occasionally later absorbed, and actual 

 recovery may take place. Mostly however the sequestrum and 

 the virus contained therein remain unchanged for a long time, 

 until the capsule breaks, for instance by a severe coughing 

 spell, whereupon the virus penetrates the surrounding lung tis- 

 sue, causing acute inflammatory changes. Sometimes the pri- 

 mary inflammatory process may come to a standstill in the 

 tissue which is not necrotic, whereupon the enclosed lobules of 

 the lungs become atrophied through shrinking of the inter- 

 lobular connective tissue. If the inflammation was confined 

 only to a small area, the process may entirely heal in this 

 manner by the formation of cicatricial tissue. 



The circulating blood does not appear to be favorable for 

 the propagation of the virus, as blood from affected animals 

 is usually not infectious, and the injection of virulent hmipli 

 into the blood circulation is also ineffective. Exceptionally 

 however the blood may contain the virus and disseminate it 



