530 



Messrs. M. Flack, L. Hill, and J. McQueen. 



amplitude diminished ; the tissue schema shrauk and hecame more rigid as 

 the resistance to flow was increased. The artery was not itself compressed 

 in this experiment, but acted as a rigid tube in its closed chamber. 



Experiment VIII. 



The flow was through two lengths of artery joined in series. Each 

 length was placed in a separate compression chamber. Tubes connected 

 the two chambers with each other and with the manometer. 



A. The tube leading from the compression chamber of the vein was closed. 

 The artery alone affected the manometer. 



A. C. B. 



Fig. 15. 



B. Both compression chambers were open, both artery and vein affected 

 the manometer. 



C. The compression chamber of the artery was closed. The vein alone 

 affected the manometer. 



"When both chambers were open the pulsatile expansion of the artery 

 was transmitted from the arterial to the venous compression chamber, and 

 partly spent itself in pulsing fluid out of the vein. When the venous 

 chamber was closed this no longer occurred, and the vein became a rigid 

 tube and no longer stored the systolic force. The diastolic pressure therefore 

 fell in the artery, and this gave a bigger swing, which acted with undivided 

 force on the recording manometer. The like result was obtained when we 

 replaced the second length of artery by a kidney, and connected the renal 

 vessels, so that the flow went through (1) the length of artery, (2) renal 

 artery, (3) renal capillaries, (4) renal vein. The effect was not obtained 

 when we substituted a length of rubber tube (rigid) for the length of artery. 



In the case of the brain or other encapsulated organ the arterial pulse 

 transmitted through the substance of the organ helps to pulse blood out of 

 the venous sinuses. In the case of the kidney urine is pumped out of the 

 collecting tubules as well as blood out of the renal veins by each pulsatile 

 expansion of the organ. 



