PLEURO-PNEUMONIA. 165 



In other instances the redness is diffused over a more or less 

 extensive surface, and is due to staining of the interlobular 

 bands by extravasated blood, one or several affected lobules 

 forming one patch, whilst the lung tissue for some distance 

 may be more or less healthy, until another patch of more or 

 less consolidated tissue is arrived at. The groups of consoli- 

 dated lobules vary much in colour, some showing the varying 

 tints of recent inflammation — blood brown, or dark brown 

 redness ; whilst others present signs that the exudation is not 

 only consolidated, but is undergoing a change of colour. We 

 have thus the red and a yellowish grey hepatization, the red 

 denoting the early, the other the more advanced stages of the 

 inflammation; but the true grey hepatization is seldom or 

 never seen now-a-days, as cattle are slaughtered before the 

 exudate has undergone this change. 



In some animals from an affected herd it has been noticed 

 that the first change is a dilatation of the blood-vessels, and the 

 lung assumes a scarlet colour. There is no exudation into the 

 interlobular connective tissue, but the lung is increased in 

 weight, and sinks farther in water than healthy lung. 



The true grey hepatization seems to indicate a drying up of 

 the inflammatory products, the formation of new connective 

 tissue in the lung, and the disappearance of the alveolar spaces ; 

 but the apparent grey or marbling hepatization seen in the 

 early stages of pleuro is due to a distended state of the 

 interlobular lymph vessels surrounding the infarction in the 

 lobule. 



The peculiarities in the character of the inflammation of 

 pleuro-pneumonia are its tendency to invade small groups of 

 lobules, more especially those composing the large lobes, or 

 even a single lobule, and to spread not only by diffusion, but 

 also by the invasion of non-contiguous lobules. In this respect 

 it simulates to some , extent the pulmonary inflammation in- 

 duced by the glanders poison, and is characteristic of a local 

 change depending upon a cause existent in the blood ; and 

 we may conclude that the true nature of the inflammation 

 differs from that of an ordinary one ; that it is secondary to a 

 general infected condition ; that the exudates do not tend to 

 become highly organised, but rather to become gangrenous, or 



