AND BLOOD PRESSURE 165 



effort, for after the injection of emulsions of white sand into the 

 jugular or femoral vein, grains have been found in the veins of 

 the face, liver, kidney, as well as in the vence cavae. Thus the old 

 Galenical doctrine that the blood is driven down the veins from the 

 liver to the body has a grain of truth in it. 



PLETHORA 



When freshly defibrinated dog's blood, warmed to body 

 temperature, is injected into a dog by way of the jugular vein, the 

 arterial pressure may rise with each injection some 20 to 30 mm. Hg, 

 but quickly returns to its old level. After blood to the extent of 

 3 to 4 per cent, of the body weight has been injected the arterial 

 pressure may reach the height of 170 to 180 mm. Hg, but much 

 beyond this it cannot be driven. If the transfusion be continued 

 until more than 10 to 12 per cent, of the body weight has been 

 introduced i.e. more than twice the normal blood quantum 

 significant upward and downward variations of pressure occur, 

 which presage cardiac failure. All the animals die in the course 

 of a day or so who have received over 10 to 12 per cent, of their 

 body weight. 



During each period of injection the heart being better filled 

 responds with an ampler output and raises the arterial pressure. 

 The pressure returns to its old level so soon as the injected blood is 

 swallowed up by the capillary- venous reservoirs. 



Finally, when so much blood has been introduced that the 

 vense cavse and liver have become distended, the heart becomes 

 over-loaded, and having to perform its systole in a dilated state 

 and owing to its greater output against an increased resistance, 

 begins to fail. The share of the vaso-motor system in the restitu- 

 tion of the pressure in the early stages of the experiment is made 

 manifest by dividing beforehand the spinal cord in the lower 

 cervical region. The low arterial pressure, which obtains after 

 such a lesion, is driven up by each injection until the normal arterial 

 pressure is reached and restitution of pressure between the injec- 

 tions then occurs. The falling back of the pressure after that point 

 has been reached is due to the escape of the blood from the arteries 

 into the capacious capillary-venous areas. 



It is in the small veins and capillaries and particularly in the 

 abdominal organs that the excess of blood lodges. The pressure 



