256 



CIRCULATION. 



of Marey it has given us a definite knowledge of the physio- 

 logical character of the pulse, and its modifications in certain 



FIG. 3. 



Sphygmograph of Marey. The apparatus is securely fixed on the forearm, so that the 

 spring under the screw V, is directly over the radial artery. The movements of the pulse 

 are transmitted to the long and light wooden lever L, and registered upon the surface P, 

 which is moved at a known rate by the clock-work H. The apparatus is so adjusted that the 

 movements of the vessel are accurately amplified and registered by the extreme point of the 

 lever. (MAEEY, Recherches, etc. Journal de la Physiologie, Avril, 1860, tome iii., p. 244.) 



diseases ; information which is exceedingly desirable, and 

 could not be arrived at by other means of investigation. In 

 short, its mechanism is so accurate that, when skilfully used, 

 it gives on paper the actual "form of the pulse? 



FIG. 4. 



A. A A A A A A 



V \1 U \l \l 



A A A 



Trace of Vierordt (Ibid.). 



This instrument, applied to the radial artery, gives a 

 trace very different from that obtained by Yierordt, which 



