602 Anatomy, Physiology, and Pathology of the 



all predisposing causes. If this be the case, it may be asked how 

 the empoisoned air produces its morbid results ? I answer, not 

 by its direct irritation on the membrane lining- the air-passages, 

 but by its specific action on the blood, which fluid, thus acted on, 

 does virtually by its changed condition subsequently affect the 

 pulmonary tissues. I have before stated my conviction that 

 pleuro-pneumonia is not an inflammatory disease in the strict and 

 legitimate meaning of the term. In order more distinctly to 

 explain my view of the manner in which the abnormal condi- 

 tion of the lungs is produced, I beg to direct attention to the 

 annexed sketches, which exhibit sections of the lung of the horse 

 and ox. Fig. 18 represents the lung of the horse, which on 



Fig. 18. 



A section of the lung of the horse, showing its condensed structure, and relative deficiency of the 

 interlobular areolar tissue, which is represented by the irregular dark lines scattered on its cut 

 surface. 



being compared with fig. 19 (a similar portion of the lung of 

 the ox) shows its structure to be more condensed, and a less 



Fig. 19. 



A section of the healthy lung of the ox, with its lobules and interlobular or connecting areolar 

 tissue. a, a. The lobules. h, b. The interlobular areolar tissue. 



amount of areolar tissue to enter into its composition. In the 

 anatomical portion of this lecture, mention has been made of 

 the lobules of the lungs and their connexion to each other by 

 areolar tissue, designated the interlobular tissue. The lobules in 

 the ox are much more distinct, and they are also very loosely 

 joined together, consequently a much larger proportion of the in- 

 terlobular tissue exists here than in the horse. This excess of 

 the connecting medium when infiltrated with the colourless por- 

 tions of the blood, gives rise to those light-coloured or yellowish 

 bands which intersect the lungs in all directions in pleuro-pneu- 



