CHAPTEE III. 

 GANGEENE, BUENS AND SCALDS. 



Gangrene may in general be said to be due to (1) obstruction 

 to veins alone, (2) obstruction to arteries alone, (3) obstruction 

 to both veins and arteries, and (4) obstruction to capillaries. 



Gangrene occurs much more commonly in the lower extremity 

 than in the upper, this being due to the fact that the farther 

 removed a part is from the heart, the less vis a tergo there is to 

 drive blood to it, and the greater the difficulty of return of blood 

 from it. The least vascular structures, such as fascial and areolar 

 tissue, slough most readily. 



Obstruction to Veins alone is not often seen in the extremities, 

 but a typical example is the death of a loop of intestine in 

 strangulated hernia. Here the pressure from without, while not 

 sufficient to cut off the entrance of blood through the arteries, is 

 ample to prevent the proper return through the veins : hence 

 the tissue of the bowel becomes more and more congested and 

 deprived of its proper nutrition in consequence of the inter- 

 ference with the circulation through its vessels, and gangrene 

 will inevitably result if the pressure is not removed early 

 enough. 



Septic thrombosis of the main venous channel of a limb, as, 

 for instance, of the common femoral or of the subclavian vein, may 

 lead to rapid moist gangrene, but slowly formed aseptic clotting 

 within the vessel may merely tend to passing or perhaps 

 permanent venous congestion. 



Obstruction to Arteries alone is perhaps most commonly due to 

 emboli which, becoming detached from the heart, block the vessel 

 at certain points. Should the occluded artery be a terminal or 

 end vessel, with no collateral anastomosis, gangrene is almost 

 inevitable. A good example is that of embolic obstruction of 



C.A.A. 3 



