1906.] Obstruction of the Vence Cavce and the Portal Vein. 279 



peritoneum. Complete ligature will only produce a small amount of dropsy 

 of the peritoneum and small haemorrhages into the mesentery. 



It is probable that constriction of the inferior vena cava must be carried to 

 ■a rather greater relative extent than that of the portal vein to produce dropsy, 

 because the anastomoses are more readily established in the case of the former 

 than in that of the latter. 



(b) Upon the Circulation of the Blood. 



The effects of obstruction of the portal vein, as is well known, are a marked 

 fall of arterial blood - pressure (3) and a rise of venous pressure in the 

 splanchnic territory. 



After complete ligature of the portal vein I have found that the venous 

 pressure in the territory of this vein, although it rises enormously behind the 

 ligature, falls to the normal limit again, as in the case of the inferior and 

 superior venae cavae, and the small amount of free fluid found in the 

 peritoneum is formed whilst the portal pressure is normal. Small haemor- 

 rhages may be produced whilst the portal pressure is raised, but the dropsy 

 is produced after the venous pressure has reached its normal limit. 



After constriction of the portal vein to 2 mm. diameter, dropsy of the 

 peritoneum is produced within 24 hours, but this may subsequently disappear 

 and complete compensation be established, the arterial and venous pressures 

 being normal. 



5. Effects of Obstruction of the Superior, together with the 

 Inferior, Yena Cava. 



(a) Upon the Production of Dropsy. 



The superior vena cava was constricted, and after an interval of 14 or 

 20 days the inferior cava was constricted, or, vice versa, the superior vena cava 

 was constricted in an animal whose inferior vena cava had been constricted 

 14 or 20 days previously. In some cases the azygos vein was ligatured at the 

 same time as the superior vena cava was constricted. 



The post-mortem findings, both the superior and inferior cavae being con- 

 stricted, are exactly the same as I described in my former paper as resulting 

 from constriction of the pericardium, in other words, the condition is exactly 

 comparable to that resulting from an uncompensated heart lesion. 



Dropsical fluid is found in each pleural cavity, in the peritoneal cavity, 

 and in the mediastinum. 



If the inferior cava be constricted to a diameter of 4 mm., the superior to 

 that of 3 mm., and the azygos vein be ligatured, the animal may survive, and 

 a month later no fluid whatever be found post mortem. 



