156 



THE BLOOD AND ITS CIRCULATION. 



the elasticity changes the jerky movement of the blood into 

 a regular movement) ; but if the muscle is paralyzed, and 

 thus has lost its perfect elasticity, the gradual transformation 

 of the intermittent shock into a continuous movement ceases; 

 and we find that jerks occur in the smallest arteries, and 

 even in the capillaries, as has been observed in the mesentery 

 of the frog ; the same takes place in inflamed tissue, and 

 there are few persons who have not experienced the arterial, 

 or rather capillary pulsations of a whitlow. 



In all this, the pulsation, the arrival of a wave, must not 

 be confounded with the movement of the circulation of the 

 blood itself; we cannot repeat too often, unda non est 

 materia progrediens, sed forma material progrediens : Czer- 

 mak has proved, by very close examination (sphymographe 

 a miroir), that, while the rapidity of the movement of the 

 blood diminishes as we approach the capillaries (see page 

 132, above), the speed with which the pulsative wave is 

 propagated increases, on the contrary, from the centre to the 

 periphery, and that it is greater in aged persons and in 

 adults than in children, showing that we must not confound 

 the pulse, its rapidity and form, with the rapidity of the 

 blood and the activity of its circulation. Onirnus, in his 

 Etudes sur les traces obtenus par le sphygmograp/ie (Journal 

 d'Anatomie, 1866), has dwelt especially on these features of 

 the pulsative wave. 



The waves of the blood column may be ascertained by 

 placing a manometer in communication with the vessel : 

 alternate rising and falling is then 

 easily observed. Efforts have been 

 made to count these undulations by 

 means of Ludwig's Jcymographion 

 (Fig. 52), which is only a moditi ca- 

 tion of the hemodynamometer de- 

 scribed above. On the surface of 

 the mercurial column of the manom- 

 eter (in a, Fig. 52) is placed a small 

 float, having on its upper face a ver- 

 tical stem (#), articulating with a 

 second horizontal stem (c), furnished 



Fig. 52. with a point, which touches a turninsf 



Lndwig's Kymographion. ^.^ (D D , } blackened by Bmok 



If this cylinder were immovable, the style would trace ver- 

 tical lines; but, as it turns regularly, the lines traced are 

 undulating, and, according as their convexity is in an up- 



