THE CIRCULATION OF THE BLOOD 521 

 THE BLOOD- PRESSURE 



The Relation of Peripheral Resistance to Blood- 

 Pressure. Eevolve the disk of the artificial 

 scheme at a rate that will produce a continuous 

 outflow. 



With each successive stroke the portion of 

 liquid unable to pass the resistance during the 

 stroke and the succeeding interval is added to 

 that left behind from preceding strokes. The 

 arteries become more and more full. The arte- 

 rial manometer registers a higher and higher 

 pressure. At length the pressure ceases to rise. 

 The mercury remains at a mean level broken by 

 a slight accession at each stroke. The pump 

 now merely maintains the constant high arterial 

 pressure. This pressure suffices to drive through 

 the resistance during each stroke and the suc- 

 ceeding interval all the liquid received from the 

 pump during the stroke. 



The venous pressure remains very low. The 

 capillary resistance (to which must especially be 

 added the resistance of the smallest arteries) 

 almost entirely exhausts the pressure in the 

 arteries. Hence the sudden and profound dif- 

 ference observed between the arterial and the 

 venous pressure. A second arterial manometer 

 placed near the aorta would show that the 



