290 



FUNCTIONS OF NUTRITION. 



lowed by a gradual descent corresponding with the collapse of the 

 artery, until it reaches the lowest point of the trace, when the ascend- 

 ing movement again takes place, and so on alternately. The line of 

 descent is marked by one, two, or three slight undulations, indicating 

 a corresponding variation in the tension of the artery during its col- 

 lapse. 



These undulations in the line of descent, in the sphygmograph 

 tracing, are due to an oscillation in the mass of the blood, subse- 

 quent to the impulse of the heart, and during the reaction of the arte- 

 rial system. Marey* has shown that similar oscillations are produced 

 when any incompressible liquid is driven by a sudden impulse into 

 an elastic tube ; and that they may be indicated by a similar movement 

 of the index of a sphygmograph. When the heart's impulse is moder- 

 ate, and the tension of the arterial system fully developed, the undula- 

 tions in the descending line of the pulse are not very perceptible ; 

 but when the heart's impulse is more rapid, and the arterial tension 

 diminished, the undulations become more marked. Traces of different 

 form, in this respect, may be produced in the same individual by arti- 

 ficial variations in the temperature of the body. The following are 

 three traces of the radial pulse obtained in -his own person by Marey, 

 by increasing the quantity of clothing at intervals of twenty minutes : 



FIG. 69. 



FIG. 70. 



FIG. 71. 



VARIATIONS OF THE RADIAL PULSE, under the influence of increased temperature. (Marey.) 



Dicrotic Pulse. In certain conditions, accompanied by rapid pulsa- 

 tion of the heart with diminished arterial tension, the secondary oscil- 

 lation of the artery becomes so marked, in proportion to the original 

 impulse, that it is perceived by the finger, and thus the pulse is ap- 

 parently doubled ; that is, there are two pulsations of the artery 

 for each contraction of the heart, namely, one due to the original 



Physiologie Medicale de la Circulation du Sang. Paris, 1863, p. 266. 



