The Measurement of Arterial Pressure in Man. 525 



H 2 the outflow ceased to pulse and was reduced to fast drops. The artery 

 then appeared flattened all along its length, but its end proximal to the 

 pump was slightly expanded by each systolic wave. At 87 cm. H2O drops 

 still escaped from the outflow nozzle. 



Experiments on excised arteries have been undertaken* to test the 

 correctness of the obliteration method of measuring the systolic blood 

 pressure, and the complete cessation of outflow has been taken as the index 

 of obliteration. Wrong conclusions have thus been drawn as to the power of 

 the arterial wall to resist compression. The disappearance of the pulse at 

 the distal end must be taken as the index of obliteration, not the absolute 

 cessation of outflow. 



Experiment V. 



The flow was through (1) a length of artery, (2) tissue schema, (3) a second 

 length of artery acting as vein. All these were placed in the same compres- 

 sion chamber, and this connected to the recording manometer (fig. 8). The 



Fig. 8. 



tissue schema was not tightly packed with chopped sponge, and the pulse 

 travelled through it to the vein. 



On compression the vein first flattened and gave a maximal pulsation, 

 while the artery became taut, then the tissue schema shrank. The outflow at 

 this period was partly due to the water expelled from it. The recorded pulse 

 now became very small as the whole system (artery, tissue schema, vein) was 

 raised up to the diastolic pressure and approximated to a rigid system. 

 Finally, the diastolic pressure was overtopped in the artery, and this gave a 

 maximal pulse (fig. 9). 



* Herringham and Womack, 'Brit. Med. Journ.,' 1908, B, p. 1614. 



