Rate of FrojJaqation of Venous Pulse. 207 



Hiirthle's venous manometers which were used in the 

 experiments consist of small metallic tambours, 10 mm. in 

 diameter, covered over with thin rubber tissue slightly 

 stretched. On the centre of this membrane rests a light 

 metal disc of 8 mm. diameter, which supports, and trans- 

 mits its movements to a lever moving very easily and 

 writing at one end on the kymograph with a suitably 

 shaped quill. The lever magnifies the up and down 

 movements of the disk as 120:5. 



On account of the Very slight variations in pressure 

 underlying the venous pulse, friction has to be minimized 

 as much as possible. This is accomplished by adjusting 

 the lever against the kymograph by a screw arrangement, 

 so that it exerts the slightest possible pressure upon it. 

 The manometers, the glass canulas, and the rubber tubing 

 connecting them were filled with saturated solution of 

 magnesium sulphate, which prevented the clotting of the 

 blood in the vein over the opening of the canula. 



It was possible, by measuring the distance that the 

 lever of the manometer was raised, and comparing this 

 with the effects of known pressures of water at the close 

 of the experiments, to estimate approximately the pressure 

 present in the veins at any point represented on the 

 tracings. 



Fig. 2. — Pressure tracing from artery (above) and brachial vein (below). 

 Time in seconds. From a dog. 



The rate of propagation was measured in two regions : 



1. Through the external jugular vein. 



2. Through the inferior vena cava to the femoral vein. 

 In the first case, pulse tracings were taken simultane- 



