647 



tend into the mucous membrane, but do not in any way anastomose 

 with the proper vascular plexus belonging to this structure. 



III. The bronchial artery also freely supplies the walls and pro- 

 cesses of the leaflets with arterial blood. 



IV. Some small branches arrive at the surface of the lungs, being 

 conducted thither by some minute bronchial tubes, which communi- 

 cate with longitudinal air-passages to be found in the substance of 

 the pleura. These small arteries anastomose freely with other 

 branches of the same artery in the sub-pleural cellular tissue. 



The bronchial artery forms no sort of anastomosis with the pul- 

 monary system in any part of the lungs, and is quite incapable of dis- 

 charging the function of the latter under any circumstances whatever. 



The bronchial veins are of two sorts : one forms a very free system 

 of inosculation on the surface of the lungs, the other is always dis- 

 coverable (in the recent lung) in the loose cellular tissue surrounding 

 the bronchial tubes : they both have valves, and consequently cannot 

 be injected in a retrograde direction, but they can both be injected 

 from the bronchial artery. Neither of them can be injected under 

 any circumstances from the pulmonary system. They both have 

 large intercommunicating trunks. 



The pulmonary artery accompanies the bronchial tube, dividing 

 precisely as it divides ; wherever there is a bronchial tube, however 

 small, there is likewise a corresponding pulmonary artery, and never 

 more than one. It gives off no branches to any collateral structure, 

 and it forms no inosculations either with its own branches or with 

 any other vessels ; every portion of it ultimately reaches the leaflets, 

 and there it makes a most minute, uniform and equal reticulation, 

 anastomosing throughout the lung. 



The pulmonary vein commences by tufts in the interior of the 

 leaflets ; part of the capillary vessels emerges on to the surface of the 

 leaflet, and commences the formation of minute veins, which imme- 

 diately dip down through the sulci which divide the leaflets, to reach 

 the interlobular surfaces, where they increase in size, and ultimately 

 come into contact with the under surface of a bronchial tube : the 

 other part of the capillary vessels makes its way from the interior of 

 the leaflet by means of the pedicel, and reaches the mucous mem- 

 brane, where a most abundant, minute, and exceedingly regular plexus 

 is formed, occupying the whole surface of the mucous membrane. 



