1906.] Obstruction of the Vence Caves and the Portal Vein. 277 



Portal Vein.. — Whether the inferior vena cava be completely occluded or 

 constricted to 2 mm. in diameter, the pressure in the portal vein rises, in the 

 former case about 90 mm., in the latter 50 to 60 mm. MgS0 4 solution. The 

 pressure falls to the normal limit again in about the same time as it does in 

 the case of the inferior vena cava. On the following day, when ascites is 

 present, the 'pressure in the portal vein is still normal. 



The following experiment shows the effects of obstruction of the inferior 

 vena cava in the chest upon the pressure in the splenic vein. 



Oct. 1, 1906. Cat; weight, 2535 grammes. Morphia, j- grain. Ether and 



artificial respiration. 



Pressures. 



Carotid artery. 



Splenic vein. 



Before obstruction 



After complete obstruction 



2 minutes later 



2 „ „ 



1 „ „ 



Obstruction removed 



1 minute later 



■*• jj >} 



£ „ „ 



Complete obstruction, 2nd time 



2 minutes later 



2 „ 



1 „ . „ 



Obstruction removed , 



2 minutes later 



1 



120 mm. 

 60 

 44 



Hg 



80 mm. Hg 



90 mm. Hg 

 42 



88 mm. 

 86 



Hg 



113 mm 



200 



175 



133 



115 



77 



90 

 114 

 113 

 170 

 177 

 135 

 115 



85 

 120 

 113 



MgS0 4 solution 



External Jugular Vein. — When the inferior vena cava is obstructed to 

 2 mm., the pressure at the upper end of the external jugular vein falls to 

 the trifling extent of about 10 or 15 mm. MgS0 4 solution. This fall indicates 

 an abstraction of blood from the territory of the superior vena cava, on 

 account of the accumulation of blood in the portal area. 



The following experiment shows that on obstructing the inferior vena 

 cava in the chest the pressure in the external jugular vein falls : — 



Oct. 18, 1906. Cat ; weight, 2750 grammes. Morphia, f grain. Ether and 



artificial respiration. 



Pressures. 



Carotid artery. 



External jugular vein. 



Before obstruction 



74 mm. Hg 

 32 



70 



56 mm. MgS0 4 solution 

 25 



56 



Directly after complete ob- 

 struction 

 Obstruction removed 







