606 Anatomy^ PJiysiology^ and Pathology of the 



vessels, and finds its way into the areolar tissue of the lunj2:s, 

 accumulatino: where this tissue exists in greater abundance, namely, 

 in the interlobular spaces. This inordinate transudation seems to 

 depend on a tendency in the blood to separate into its several con- 

 stituents, arising most likely from the diminished vital force of the 

 fibrine, and an arrestation to the conversion of the albumen of the 

 serum into fibrine. The fibrino-albuminous portions of the fluid 

 are thus changed, and probably also augmented, and their exudation 

 is a natural consequence of such condition. The red corpuscules, 

 being in part deprived of the liquor sanguinis in which they float, 

 are retained in the capillaries, where they accumulate in un- 

 limited numbers, obliterate their passage, and compress the air- 

 cells they surround, so as to stay the entrance of the air, and 

 produce, as elsewhere stated, the dark-coloured spots which stud 

 the lungs. It is these effusions and the obliterated condition of 

 the vessels which give bulk, increased weight, and solidity to the 

 lunofs, and destroy their function as aerifying organs. 



From this explanation it is evident that I regard pleuro- 

 pneumonia to approach nearer to a dropsical than to an injlaifn- 

 matory disease. The lungs, if examined at the commencement of 

 the affection, will show that the morbid action commences here 

 and there in their substance, and that these patches quickly 

 increase in size so as to run into each other. We have also 

 frequent opportunities of verifying these remarks in animals 

 which have died in the advanced stages of the malady, from 

 the circumstance that one lung is principally affected, the other 

 exhibiting the beginning of the disease. Fig. 22 is inserted 

 for the purpose of rendering this description more evident. 

 The spots marked a a represent the tumified portions of the 



Ficr. 22. 



Lung, showing the commenceir.ent of pleuro-pneiimonia. 

 a. Elevated spots produced by effusion. b. A cut carried through one of the spots, to demon- 

 strate the nature of the change producing it. 



