26 CANINE MEDICINE AND SURGERY 



present the features of ordinary red or gray hepa- 

 tization. 



Further, by an extension of the disease, the 

 neighboring diseased' areas may coalesce and thus 

 extensive tracts of lung tissue become involved. 

 Full lobular pneumonia is always secondary to the 

 blocking up of air passages, and especially those 

 of capillary size; it may be excited either by the 

 gradual extension of the inflammatory process from 

 the tubes to the air vesicles, or by the entrance 

 into the vesicles during inspiration of the inflamma- 

 tory products of the tubes, which then act as irri- 

 tants and carriers of infection. 



Closely related to lobular pneumonia is the dis- 

 seminated pneumonia due to obstruction of small 

 branches of the pulmonary artery, either by em- 

 bolism or thrombosis, or in the course of pyemia. 

 In these cases, as in the other, the affected areas 

 are of small size and limited by the margin of the 

 lobules. But there is a greater variety of result, 

 especially in pyemia ; in which, while the affected 

 areas sometimes present simple hyperemia, or red 

 or gray hepatization, they not infrequently are the 

 seat of hemorrhage, or undergo rapid suppuration 

 or gangrene. 



In all forms of pneumonia, even in such as are 

 not of bronchitic origin, there is a tendency to the 

 development sooner or later of bronchitis. But 

 apart from this there is a marked disposition early 

 in the course of pneumonia to the effusion into the 

 tubes from the inflamed air cells of a transparent, 

 very viscid fluid, uniformly stained with blood and 

 containing cells ; and in some rare cases this fluid, 

 like that in the air cells whence it is derived, under- 

 goes coagulation in the bronchial tubes, which thus 



