ADVANCED EXPERIMENTAL PHYSIOLOGY 163 



probably the cause of such disturbed action. While the record is being 

 taken place both hands on the subject's belly and compress the 

 abdomen ; both venous and arterial pressures rise. The rise in arterial 

 pressure may be measured with the sphygmometer. 



One tambour is now placed over the carotid and another over 

 the cardiac impulse. The beginning of the impulse curve marks 

 the beginning of the ventricular contraction. The beginning of the 

 carotid pulse curve marks the beginning of the period of systolic out- 

 put and the opening of the aortic valves. Between these points is the 

 period of rising tension, when the ventricle is raising the blood pressure 

 up to that in the aorta. The beginning of the dicrotic notch cor- 

 responds with the closure of the aortic valves and the end of out- 

 put. The time lost in the transmission of the pulse-wave from the 

 heart to the carotid artery should be deducted in making these time 

 measurements, but it is almost negligible. In a man with a pulse 

 frequency of 70 the duration of systole was 0-379 sec., of diastole 0-483 

 sec. It is interesting to repeat the observations after the frequency of 

 the heart has been accelerated by running up and down stairs. The 

 diastolic period is shortened much more than the systolic period. When 

 the pulse varied in the proportion 100 : 270 the duration of a systole 

 varied in the proportion 136 : 100. 



With the two armlets and mercurial manometer and syringe 

 bulb measure the systolic pressure in the arm and leg using the 

 radial and posterior tibial or dorsalis pedis arteries as indices of the 

 obliteration of the pulse. Let the subject be horizontal. Repeat after 

 the subject has run up and down stairs, and again after he has put 

 one hand in hot water for some minutes. The pressures which were 

 equal will now appear unequal for the artery softened by the effect 

 of heat conducts the pulse less well. In cases of aortic regurgitation 

 the leg and arm readings are unequal, the leg being the higher owing 

 to the leg arteries being stiffer and conducting the wave better. 

 Measure the pressure in the leg and arm (1) with the subject lying 

 horizontal, (2) with the legs raised in the L-shaped position, (3) stand- 

 ing erect, the observed leg being kept in an easy relaxed position and 

 the weight thrown on the other leg. In each case measure the difference 

 in height between the upper edges of the armlets with the metre rule. 

 Calculate the difference in terms of mercury by dividing by 13, and 

 compare the difference in the readings found with the calculated differ- 

 ences. The pressure differs by the column of blood separating the two 

 points of measurement. The compensatory vasomotor mechanism keeps 

 the pressure in the aortic arch and its branches about the same in all 

 three postures, while the pressure in the leg arteries varies greatly. 



