vin BLOOD-STREAM: MOVEMENT IN VESSELS 265 



distinguished. The former, produced by the pulse-wave which 

 starts from the aorta, usually reaches its culminating point 

 without interruption ; the latter, on the contrary, shows several 



is 



Fie. 103. Marey's direct spliygmograph, applied to the radial artery. 



oscillations, one of which (the second, expressed in a rise preceded 

 by a slight depression) is rarely absent in pulse tracings. It 

 known as the dicrotic wave, and con- 

 sists in a negative wave (dicrotic 

 notch), immediately followed by a 

 secondary positive wave. 



It has been proved by innumer- 

 able control experiments of Buisson, 

 Marey, Landois and others, that the 

 sphygmograms thus obtained do really 

 reproduce the form of the pulsatile 

 oscillations of blood pressure, and that 

 their constant dicrotisni is no factitious 

 product of the registering apparatus. 

 Here we need only say that sphygmo- 

 grams obtained with the sphygmoscope 

 or other elastic manometers (Fig. 67, 

 p. 205) present the same dicrotic form. 

 Moreover, as Landois showed, it is 

 possible to obtain autosphygmograms, 

 by dividing the artery of an animal, 

 and directing the rhythmical jet of 

 blood against a rotating drum covered 

 with filter -paper (haemautography). 

 As shown by Fig. 104, the form of the 

 haemautograni agrees perfectly with 

 those from the sphygmograph and sphygmoscope ; 

 dicrotic wave is even more apparent, this being the only 

 important feature of the pulse curve that we need consider. 



Since the dicrotic wave persists, and is even more pronounced 

 in autosphygmograms, it is proved to be the result of a positive 



FIG. 104. Auto-sphyginograin (Haem- 

 autogram) from posterior tibial 

 artery of large dog. (Landois.) p, 

 Primary wave ; </, dicrotic wave. 



while the 

 really 



