INTUMESCENTI^l. 583 



pressing the vena cava, may produce an anasarca of the lower 

 extremities. It is indeed true, that scirrhosities of the spleen 

 and other viscera have been frequently discovered in the bodies 

 of hydropic persons ; but I believe they have been seldom found 

 unless when scirrhosities of the liver were also present ; and I 

 am inclined to think, that the former have been the effects of 

 the latter, rather than the cause of the dropsy ; or that, if 

 scirrhosities of the other viscera have appeared in hydropic bo- 

 dies when that of the liver was not present, they must have 

 been the effects of some of those causes of dropsy to be here- 

 after mentioned ; and consequently to be the accidental attend- 

 ants, rather than the causes of such dropsies. 



MDCLIII. Even in smaller portions of the venous system, 

 the interruption of the motion of the blood in particular veins 

 has had the same effect. Thus a polypus formed in the cavity 

 of a vein, or tumours formed in its coats, preventing the free 

 passage of the blood through it, have had the effect of produc- 

 ing dropsy in parts towards the extremity of such veins. 



MDCLIV. But the cause most frequently interrupting the 

 motion of the blood through the veins is, the compression of 

 tumours existing near to them; such as aneurysms in the arteries, 

 abscesses, and scirrhous or steatomatous tumours in the adjoin- 

 ing parts. 



To this head may be referred the compression of the descend- 

 ing cava by the bulk of the uterus in pregnant women, and the 

 compression of the same by the bulk of water in the ascites ; 

 both of which compressions frequently produce serous swellings 

 in the lower extremities. 



MDCLV. It may be supposed that a general preternatural 

 plethora of the venous system may have the effect of increasing 

 exhalation ; and that this plethora may happen from the sup- 

 pression of fluxes, or evacuations of blood, which had for some 

 time taken place in the body, such as the menstrual and hse- 

 morrhoidal fluxes. A dropsy, however, from such a cause, has 

 been at least a rare occurrence ; and when it seems to have 

 happened, I should suppose it owing to the same causes as the 

 suppression itself, rather than to the plethora produced by it. 



MDCLVI. One of the most frequent causes of an increased 

 exhalation, I apprehend to be the laxity of the exhalent vessels. 



