160 THE VASCULAR SYSTEM 



studied the result of totally obstructing and of narrowing the 

 venee cavse in order to arrive at the share in the production of 

 dropsy which increased capillary pressure had. He tried at first 

 to produce cardiac deficiency by constriction of the pericardium by 

 means of sutures, so as to prevent the proper diastolic expansion 

 of the heart, but gave up this line of work as he found it very 

 difficult to hit the right amount of constriction. The animals 

 either died or recovered without symptoms. To obstruct the 

 venae cavse he made an incision one to two inches long parallel to 

 the ribs in the third right intercostal space for the superior, and 

 seventh space for the inferior cava. Artificial respiration was put 

 on, the ribs drawn apart by retractors and the lung held aside by a 

 spatula, and incomplete obstruction set up by encircling the vein 

 with a short piece of soft rubber catheter of appropriate diameter. 

 The thorax was then closed, after squeezing out the air, and the 

 animal allowed to recover. The venous pressures were measured 

 in some of the animals after varying degrees of constriction had 

 been established, the measurements being taken in the external 

 iliac ; at the lower end of the femoral above the ankle ; in the 

 splenic branch of the portal ; and in the post-auricular branch of 

 the external jugular. Complete occlusion of the superior cava 

 caused the death of the animal in one to six days. There was 

 caused considerable oedema of the mediastinum and exudation of 

 venous fluid in the pericardial and pleural sacs. The animal 

 refused food, wasted, and passed less urine. When the obstruction 

 was made above the azygos vein, one animal survived, efficient 

 anastomoses becoming established by way of the internal mammary, 

 azygos, veins of diaphragm and comes nervi phrenici. There was 

 oedema and fluid in the pleura and pericardium until these 

 anastomoses were established properly. Another animal died 

 eighteen days after operation, and 145 c.c. of fluid were found in 

 the right and 125 c.c. in the left pleural cavity. In the cases of 

 partial obstruction Bolton found constriction to three-fifths of the 

 normal size produces oedema and hydrothorax. 



Such obstruction only raises the venous pressure in the external 

 jugular by 20 to 40 mm. of blood, and quite temporarily. Com- 

 plete obstruction altered the arterial pressure very slightly and 

 raised the pressure in the external jugular by 130 mm. of blood, 

 but within an hour the pressure was normal again. The oedema 

 and dropsy were produced next day long after the pressure had 



