MORBID ANATOMY 8 1 



lines usually arranged in curves and circles. These, so far as 

 determined, represent the cut outlines of the interlobular and 

 peribronchial tissue infiltrated with cells. It has already been 

 stated that these lines may represent the paths along which 

 the swine- plague bacteria invade the lungs from the pleural 

 surface. 



The cut ends of the bronchi of the ventral lobes are fre- 

 quently occluded with thick, whitish pus ; in the other lobes 

 a reddish froth is usually present. Rarely they also contain 

 thick glairy mucus in which particles of dry pus and lung 

 worms are imbedded. The contents of the air tubes in the 

 ventral lobes may have been derived from the overdistended 

 alveoli, or else a broncho-pneumonia may have preceded the 

 swine-plague pneumonia. 



In microscopic sections of diseased luog tissue the alveoli 

 and smallest air tubes are found distended with cell masses 

 consisting chiefly of leucocytes. Usually there is very little 

 fibrin and very few red corpuscles in the alveoli, even in cases 

 in which the disease was quite recent. It may be that the 

 stage represented in ordinary croupous-pneumonia by the pres- 

 ence of fibrin in connection with the cellular elements is very 

 brief, and that it is speedily replaced by large numbers of leu- 

 cocytes. The large predominence of these elements in some 

 portions of the lungs, as well as beginning fatty degeneration, 

 is probably the cause of the regular mottling of the lungs, as 

 seen from the surface. The little yellowish hazy dots represent 

 alveoli surrounded by the hyperemic walls. 



The necrotic and caseous changes so frequent in swine 

 plague are most interesting. The latter are usually quite small 

 and disseminated in large numbers over the diseased lobes. 

 The former represent larger masses from a marble to a horse- 

 chestnut in size. They represent tissue which has been 

 destroyed by the rapid multiplication of swine-plague bacteria 

 in particular localities. Hence they are found in all stages of 

 the pneumonia. The large caseous masses may be considered 

 as the result of a slow death of larger areas of lung tissue, due 

 primarily to the gradual overdistention of the tissue by leuco- 



