264 



PHYSIOLOGY 



CHAI'. 



observations made ou these three phenomena in order subsequently 

 to compare the results. 



The so-called sphygmographie methods have yielded perfect 

 sphygmograms, which give an exact graphic representation of the 

 pulsatile oscillations of pressure. 



Even the ancient physicians, more particularly Herophilus, 

 Erasistratus, and Galen, recognised by touch some of the chief 

 characteristics of the arterial pulse, and the alterations in frequency 

 (pulsus frequens et rarus), magnitude (p. met gnus et parvus), rate 

 of dilatation (p. celer et tardus), hardness or compressibility 

 (p. durus et mollis), regularity or irregularity of rhythm (p. inter- 

 '//t ittens, alternans, intercurrens), and lastly, in the form of the pulse 

 wave (p. dicrohifi seu bis feriens). But all these and many other 

 distinctions of pulse, as laid down by Galen, are founded far too 



much on subjective 

 appreciation. Cusano 

 (1565) made a great 

 advance when he first 

 used a watch to count 

 the beats; still greater 

 progress was made by 

 Vierordt (1855) who 

 first demonstrated the 

 possibility of register- 

 ing the pulse auto- 

 matically, although his 



Fn;. 102. Marey's contrivance for transmitting the move- 

 ments of the spring to the writing-lever of the sphygmo- SpliygniOgrapll CllCl not 

 graph, m, Steel spring ; li, button compressing the artery, Q lln p apr ] 

 connected above with a little rod, of which the screw bites ' 

 into the wheel of the axis a, which moves the lever Z from 

 above downwards in the direction of the arrow. 



in giving a 

 true picture of the 

 form of the pulse-wave 

 or the pulsatile oscillations of arterial pressure. 



The first sphygmograph which accurately recorded the form of 

 the pulse was that constructed by Marey in 1860, which found 

 ready acceptance among physicians owing to the elegance of the 

 method, and the exaggerated hopes of clinical advantage that were 

 founded on it. The essential part of Marey's sphygmograph was a 

 steel spring, pressed against the radial artery by a button, which 

 transmitted the pulsations to a long and very light lever, by which 

 they were recorded exactly, in a magnified form, upon a metal 

 plate covered with smoked paper, propelled at a uniform rate by 

 clockwork. Fig. 102 shows the mode of transmitting the move- 

 ments of the spring to the lever according to the most recent 

 improvements, and Fig 103 shows the complete instrument applied 

 to the forearm. The sphygmograms obtained with Marey's 

 sphygmograph may vary considerably under different conditions of 

 health and disease ; but all have one characteristic feature a 

 rapidly ascending and slowly descending period can always be 



