890 



PHYSIOLOGY 



-velocity of the blood at the moment at which this part of the record was being taken. 

 Of course this instrument has to be calibrated if we wish to determine the velocity of 

 the blood in absolute measure. In Fig. 391 the velocity at the points 1 and 1', corre- 

 sponding to the cardiac systole, was 248 mm. per second. At 2 and 2', corresponding 

 to the dicrotic elevation, the velocity was also 248 mm. At 3 and 3', towards the end 

 of diastole, the velocity sank to 127 mm. 



The velocity of the blood in the capillaries can be measured by direct observation 

 of the capillaries under the microscope, and noting the time it takes for a blood-corpuscle 

 to move from'one edge of the field to the other. 



THE VELOCITY IN DIFFERENT PARTS OF THE 

 VASCULAR SYSTEM 



During systole the velocity of the blood in any part of the arterial system 

 must be greater than during diastole ; thus in the carotid of the horse the 



following figures were found : 



Velocity per second 



During systole . . . . 520 mm. 



During diastole ..... 150 mm. 



The following figures have been obtained from experiments on dogs 

 (Tigerstedt) : 



