PLEUKO-PNEUMONIA. 169 



lung territory are found occluded, and the lung tissue sur- 

 rounding them collapsed by the gravitation or entrance into 

 them of the degraded, softened products of the pneumonia, 

 which, having escaped from the seat of formation, have been 

 forced by the inspiratory act into the healthy tubes. Here 

 we certainly find the bronchi filled with diseased products, and 

 the pleural surface presenting little or no signs of disease ; but 

 an examination of the pneumonic products will at once prove 

 that they consist of degraded fibrinous exudates, and that the 

 parenchymatoiis disease is antecedent to the occlusion of the 

 bronchi. In the second place, Dr. Yeo concludes that, in the 

 common run of cases where pleurisy is associated with exten- 

 sive disease of the lung, the latter gives the impression that it 

 is of much older standing than the pleural affection. He says, 

 " The pleurisy is commonly acute ; while in the lung we usually 

 have evidence of such chronic change as would require a very 

 long time for their development." 



If Dr. Yeo had had clinical experience amongst cattle he 

 would have seen that these conclusions are quite opposed to 

 facts. Many instances have occurred in my experience where 

 animals, apparently healthy, which had been slaughtered in 

 consequence of having been in contact with others affected with 

 pleuro, have presented, ;post mortem, round patches of consolida- 

 tion in one or more parts of their lungs, always associated 

 with pleural exudation, and sometimes even adhesion of the 

 opposing pleural surfaces ; indeed, in some instances the most 

 pronounced evidences of the presence of the disease have been 

 patches of pleural exudation with but little or no corresponding 

 invasion of the lung parenchyma. 



Then, as to the chronicity of pleuro-pneumonia, the state- 

 ments of Dr. Yeo are against all clinical facts, and consequently 

 must not go unchallenged. A reference to the accompanying 

 woodcut (fig. 5), and a short history of the case from which it 

 was obtained, will illustrate this point. The large dark patches 

 reveal the condition of dark red consolidation, and the smaller 

 ones the commencement of that process, which is evidently that 

 of haemorrhage into the alveoli ; the dark patches are surrounded 

 by oedema of the tissue contiguous to the points of extreme 

 congestion; the interstitial tracts are much distended, and if 



