PNEUMONIA 21 



Pneumonia 



Like bronchitis, inflammation of the substance of 

 the lungs is due to infection (pneumoccoccus, or 

 Diplococcus pneumoniae, and various Streptopocci 

 and Micrococci). It may also be caused by the 

 spread of inflammation from other parts, as from 

 the bronchial tubes in bronchitis or from the pleura 

 in pleurisy. Again, it may be developed by the 

 direct action of mechanical or other irritation, such 

 as the inhalation of irritant gases or dust, or by 

 vomition ; or it may spring from the presence of 

 emboli In the branches of the pulmonary artery or 

 of tubercles or clots in the lung tissue ; it may 

 also occur as a complication of heart disease, kid- 

 ney disease, rheumatism, debilitating diseases, dis- 

 temper, tuberculosis, or echinococcosis. 



Cold and wet, unhealthful surroundings, and a 

 lowered vitality are undoubtedly predisposing 

 causes. Clinically, in the dog we have to deal with 

 two forms of pneumonia, namely, lobar pneumonia, 

 which is of rare occurrence, and lobular pneumonia, 

 which is common. The words "diffuse" and "cir- 

 cumscribed," however, might be used to better ad- 

 vantage, the type of the former variety being fur- 

 nished by the idiopathic affection; that of the latter 

 by the condition which is secondary to diseases of 

 the air passages. The two varieties, however, 

 merge into one another. 



Lobar (Croupous) Pneumonia 



This type begins with hyperemia of the small 

 vessels which are distributed in the walls of the air 

 cells and bronchial passages, a swelling and tend- 

 ency to proliferation of the epithelial cells of these, 

 parts, and an exudation of serum and cellular ele- 

 ments of the blood. The air vesicles and, passages 



