ADVANCED EXPERIMENTAL PHYSIOLOGY 161 



by the amputation wound. The carcase will continue for several hours 

 to exhibit good reflexes employing the skeletal muscles, although the 

 arterial blood-pressure is low, often not more than 80 mm. Hg. 

 The scratch and other reflexes may be studied very well on this 

 preparation. 



CHAPTER XXXIX. (Advamed). 

 THE PULSE. 



The Velocity of Transmission of the Pulse Wave. Mackenzie's 

 polygraph is used. The recording tambours write on a roll of paper 

 which is unwound by the clockwork. The writing styles are wet with 

 red ink. A time marker writes seconds. Two tambour sphygmographs 

 are taken, and one is applied to the carotid, and the other to the radial 

 artery. The recording tambours are brought to write exactly beneath 

 one another on a fast drum, and a time tracing is taken with the tuning 

 fork. Mackenzie's polygraph is most convenient for these experiments. 

 The distance between the carotid artery and the radial is measured. 

 The rate of transmission is about 5-8 metres a second. The rate of 

 transmission increases as the coefficient of elasticity of the arterial 

 wall. It is therefore greater with high than with low arterial pressure. 



The velocity of transmission from carotid to radial may be lessened 

 by placing the arm in water so as to produce vaso-dilatation. The 

 length of the pulse wave is the product of the velocity of transmission 

 by the time occupied by the wave in passing any given point. 

 Calculate this value from the record. It is about 5 metres, so the pulse 

 wave reaches the periphery before it has left the aorta. 



Jugular and Radial Pulse Curves. The jugular pulse and the radial 

 venous pulse are simultaneously recorded in man, and by this means 

 time relations of the cardiac cycle are determined. The jugular pulse 

 is recorded by means of a receiving tambour, which is pressed 

 down upon the jugular vein just above the clavicle on the right 

 side. 



The tambour is not closed by a membrane, but is pressed down 

 on the skin by the fingers until an air-tight junction is made and 

 a good tracing is obtained. The subject must lie down with his 

 head slightly raised by a cushion and bent to the right side. The 

 venous pulse shows three positive waves, A, C, and V. A marks the 

 auricular systole. C is synchronous with and chiefly caused by 

 the output of blood from the ventricles into the arteries. The carotid 



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