438 



VETERINARY PHYSIOLOGY 



ing these by means of the Riva Rocci apparatus (p. 448). 

 The character of the arterial wall modifies it very largely 

 and the true height of the pulse wave in the great arteries 

 near the heart is masked by the thickness of the arterial 

 wall. 



The pulse wave is highest near the heart, and becomes 

 lower and lower as it passes out to the periphery, where it 

 finally disappears altogether (fig. 190). This disappearance 

 is due to its force becoming expended in expanding the 

 arterial wall. 



4. The Form of the Wave. — Waves at sea vary greatly in 



Fig. 185. — Diagram of Dudgeon's Sphygniograph. CI., clockwork driving 

 the smoked paper, Tr., under the writing point of the liver, L., Sp., 

 is a steel spring, with a button, B., which is applied over the radial 

 artery. With each expansion of the artery the button is moved 

 upwards, and causes a movement of the system of levers indicated by 

 the arrows. 



form, and the form of the wave might be graphically recorded 

 on some moving surface, such as the side of a ship, by some 

 floating bod}^ If the ship were stationary, a simple vertical 

 line would be produced as the wave passed, but, if she were 

 moving, a curve would be recorded, more or less abrupt 

 according to her speed. From this curve the shape of the 

 wave might be deduced, if the speed of the vessel were 

 known. 



The same method may be applied to the arterial pulse. 

 By recording the changes produced by the pulse wave as it 



