136 BOVINE PATHOLOGY. 



" 7. The block in the lymphatics of the broncho- vascular 

 system impedes the flow of lymph from the corresponding 

 territory. 



" 8. The tributary lymph channels are thus mechanically 

 engorged, and at the same time they are irritated by 

 infective materials. 



''9. The inflammation of all the coats of the air-tube 

 gradually spreads towards the root of the lung. 



" Thus, we have a deep-seated cone of typical consolida- 

 tion, traversed by numerous wide whitish lines, corre- 

 sponding to the swollen interlobular connective tissue 

 (marbling). In fact, the essential features of the disease 

 are all established. 



" The morbid process seldom stops here however. It 

 spreads in two ways. First, by the broncho-vascular 

 lymph passages : 



" 1. The irritating and infective materials find their way 

 along the lymphatics towards the root of the lung, follow- 

 ing the normal course of the lymph stream. 



'^ 2. The wall of the bronchus becomes affected after a 

 time by the irritative matter in its surrounding lym- 

 phatics. 



" 3. The lymphatics of tributary bronchial tubes, met 

 with as the disease thus advances, are choked, and the 

 drainage of their territory impeded. 



" 4. The interlobular lymph spaces of the newly affected 

 territory soon become filled with exudation. Thus, the 

 clear kind of consolidation is produced. 



" Secondly, by the pleura : 



" 1. The pleura becomes affected over the focus of con- 

 solidation by means of the subjacent lymphatics. 



'' 2. The pleurisy soon extends far beyond this limited 

 region, or the serous membrane becomes generally in- 

 flamed. 



" 3. The inflamed pleura infective materials reach the 

 lymphatics beneath it, and also those lying between the 

 neighbouring superficial lobules. 



"4. Extending along the interlobular lympathics, the 

 irritation and exudation may pass towards the deeper 



