282 Dr. C. Bolton. Dropsy produced hy [Dec. 19, 



and develop dropsy, and in which the constriction is not very complete, 

 the raised pressure is relatively insignificant and not to be compared with 

 that occurring during muscular movement. The earliest dropsy, therefore, 

 in uncompensated heart disease is strictly local in origin, and the capillaries 

 •of the district affected become, practically speaking, an excretory organ. 

 In the remaining parts of the body absorption must occur pari passu with 

 this increased output of fluid, in order to keep up the normal amount of 

 blood in the body, but in the part affected absorption by the veins must be 

 retarded. 



As the disease becomes more extensive the area of production of the 

 dropsy must extend. 



When the superior or inferior vena cava is obstructed alone, the same 

 initial rise of pressure occurs behind the obstruction as far back as the 

 capillaries, and it soon falls to the normal level again, owing to distension 

 of the particular veins in question and also, to some extent, on account of 

 the anastomotic channels, which after many days may effect complete 

 compensation if the constriction is not too complete. The dropsy is 

 produced in exactly the same way as described above, when all the venous 

 channels opening into the heart are obstructed, and it disappears in those 

 cases in which complete compensation is subsequently effected by the 

 -anastomoses. 



Absolutely the same remarks apply to obstruction of the portal vein. 



Arc there any conditions in which the dropsy of venous stagnation is 

 produced when the capillary pressure is high ? 



In answer to this question it may be said that the necessary conditions 

 -are : Firstly, that the venous territory in which the obstruction is situated 

 be not too large in proportion to the rest of the vascular territories of the 

 body, so that sufficient blood can be spared to maintain a high venous 

 pressure, and, secondly, that the anastomoses be not too free. Under these 

 circumstances the dropsy of venous stagnation will occur with a high 

 capillary pressure, but the actual cause of the oedema is, however, an 

 alteration in the capillary wall, the high pressure being merely a concomitant 

 circumstance, or at the most a contributing factor. A parallel instance is 

 seen in the case of hemorrhagic infarction. The escape of blood from the 

 vessels in hemorrhagic infarction may occur when the capillary pressure 

 is high, as in venous obstruction, but it may also occur when the capillary 

 pressure is low, as in arterial obstruction. 



The dropsy of local venous stagnation is, therefore, produced in exactly 

 the same manner as that resulting from general venous stagnation, the 

 common factor underlying both being an altered condition of the vessel wall. 



