EFFECT OF HYDROSTATIC PRESSURE 301 



increased hydrostatic pressure it is found that the base-line is 

 shifted downwards, which in the leaflet it must be remem- 

 bered means erection. The contractile effect is also opposed, 

 hence we observe the extent of contraction gradually 



Fig. 146. — Application of increased internal hydrostatic 

 pressure at arrow. Displacement of base-line downwards 

 in the record indicates expansive erection of leaflet. 

 Enforced expansion also causes decline in the extent 

 of systolic contraction. 



decreased, with the result that a line joining the apices of 

 the successive pulsation slopes downwards (fig. 146). 



Effect of Load 



We will next study the effect of load. Different weights 

 are placed on the second arm of the lever. The effect of 

 the weight is to pull the leaflet slightly upwards. This 

 pull will have the effect of opposing the contractile 

 movement. 



I took a series of records of the pulsation of Desmodium, 

 first without any weight, then with increasing loads of ^wo' 

 T fj5-, and -5^ grm. (fig. 147). It will be seen that the am- 

 plitude of pulsations is in consequence progressively 

 diminished. Without load, the amplitude is 19 mm. ; 

 under a load of T Jog rm - it has become reduced to n mm. ; 



