AND BLOOD PRESSURE 161 



become normal again. Complete obstruction of the inferior cava 

 caused death in a few hours (as was determined by R. Lower in 

 the days of Charles II.). The arterial pressure at once fell to 

 30 to 40 mm. Hg, and the venous pressure in the external iliac 

 rose by 100 mm. of blood or more, but within an hour fell back to 

 its old level. 



Partial constriction to more than three-fifths caused death. 

 The diameter of the vena cava is about 5 mm., and on constriction 

 to 3 mm. the animal survived, while on 2 to 2 mm. it might or 

 might not die. The arterial pressure fell about 20 mm. Hg when 

 the constriction was to 3 mm., and the pressure in the external 

 iliac vein rose 20 to 30 mm. of blood, but this rise was quite tem- 

 porary. Ascites resulted until proper anastomoses were established 

 by way of the veins of the abdominal wall ; but the first signs of 

 ascites occurred long after the venous pressure had returned to 

 normal. Constriction of the portal vein from its normal diameter 

 4 mm. to 1 mm. gave the same results as constriction of the 

 vena cava inferior. Constriction of both cavae to 3 mm. produced 

 dropsy of the pleurae and peritoneum just as in a case of uncom- 

 pensated heart disease. 



Finally Bolton observed that 130 c.c. physiological saline (an 

 amount equal to from two-thirds to the whole blood quantum) 

 might be slowly injected in the course of one and a half hours, the 

 blood pressures remaining normal, and some ascites being produced 

 meanwhile. 



In the experiments on the effect of complete obstruction of the 

 inferior vena cava he records that while the pressure in the external 

 iliac vein rose by 100 mm. of blood or more, that in the femoral 

 vein above the ankle only rose by some 60 mm. The writer 

 attributes this to the low pressure in the arteries, the derivation 

 of the arterial blood through the lower resistance channels the ab- 

 dominal vessels and consequent slow filling of the veins of the legs. 



Bolton's observations show that the ascites and oedema occur 

 when the general venous and arterial pressures are normal. They 

 must be ascribed, therefore, to altered tissue metabolism, greater 

 filling of and stasis in capillary areas, and consequent change in 

 the conditions of surface and osmotic energy. 1 



1 The work of 15. Moore and his co-workers has shown how the osmotic pressure 

 of the complex of colloids and crystalloids which forms the serum or tissue proteid 

 is altered by slight changes in alkalinity, Ac. See Bio-Chemical Journal, vol. iii. 

 p. 122, 1908. 



L 



