104 LABOR A TOR Y G VIDE IN PH YSIOLOG Y. 



If not, why? What allowance, if any, should be 

 made for this? 



b. Arterial pressure. 



(5) With capillaries 1 to 6 open and tubes 7 and 8 

 closed, let one member of the division make strong 

 rhythmical contractions of the bulb at the rate of 

 about 2 per second. Note effect on manometer. 

 Account for all the phenomena. 



c. Venous pressure. 



(6) Note the effect of the contraction upon the venous 

 manometer. If there is any change in the manome- 

 ter, compare in rhythm and in extent with the 

 changes in the arterial manometer. 



d. Relations of arterial to venous pressure. 



(7) Make very slow contractions. Note results. 



(8) Make rapid, strong contractions. Note results. 



(9) Make rapid, weak contractions. Note results. 



(10) Remove the clamps from vessels 7 and 8 (local 

 dilatation of arterioks) and repeat experiments 7, 8 

 and 9, noting and interpreting results. What effect 

 does a dilatation of arterioles have upon venous 

 pressure? What effect does it have upon arterial 

 pressure? 



e. Pressure formula. 

 Let: P ^pressure. 



Pa ^arterial pressure. 

 Pv =venous pressure. 

 H ^strength of contractions. 



Rd = distal resistance beyond point of observation. 

 v =velocity at point of observation, 

 r ^radius of vessel at point of observation. 

 How many of the following formulae will your observa- 

 tions justify? 



