CIRCULATION OF THE BLOOD. 533 



fifteen times the body weight, will be set in motion by the contractions 

 of each ventricle, or 37,620 pounds in all. If it be admitted that the 

 amount of blood in the ox is ^ of the body weight, or 52.18 pounds, 

 and each systole propels 0.15 liter, or 1J pounds of blood, thirty-five con- 

 tractions of the heart would be needed to drive the entire amount once 

 around the body ; or, the pulse-rate being 50 per minute, the circulation 

 would be completed in forty-two seconds. It is evident that these figures 

 are in opposition to the estimates obtained by Hering's method, which, 

 according to Vierordt, places the duration of the circulation as equal to 

 the time required by the heart for making twenty-seven pulsations.* 



The Pulse. — As the left ventricle empties itself into the aorta it is 

 compelled to overcome the pressure of the blood already contained in 

 the arterial system and two phenomena result — an acceleration of the 

 current of blood toward the capillaries and the dilatation of the aorta to 

 accommodate the additional amount of blood thrown in by the ventricle. 



In the description of the physical principles concerned in the pas- 

 sage of fluid through an overfilled system of tubes with elastic walls, 

 it was stated that at each introduction of fluid a wave was produced 

 which rapidly traversed the walls of the tube, its velocity of movement 

 being proportional to the tension of the walls of the tube, while its cause 

 was found not in the passage of the fluid, but in an up-and-down oscilla- 

 tion of the walls of the vessels. Such a wave of oscillation as seen in 

 the arterial system is described as the pulse. The pulse is, therefore, 

 the diastole of the arteries. In the arteries which are close to the heart 

 this diastole is almost synchronous to the systole of the ventricle, but as 

 the distance from the heart increases a sensible interval may be recog- 

 nized between the contraction of the ventricle and the appearance of the 

 pulse-wave. This time is required for the transmission of the wave 

 through the walls of the vessels. To determine the time required for the 

 transmission of this wave it is only necessary to estimate the interval of 

 time elapsing between the contraction of the heart and the appearance of 

 the pulse-wave in any locality. This time, together with the distance 

 of the point examined from the heart, will enable us to calculate the rate 

 of movement of the pulse-wave. It has been found that the transmission 



*It is probable that the data on which the above calculations are made are not even 

 approximately correct, though they may perhaps serve to give a general idea of the subject. 

 For experimental proof as to the different sources of error in Hering's method and the 

 mode of calculating the amount of blood thrown out in the contractions of the ventricles, 

 see papers by the author — "A New Method for Determining the Amount of Blood Thrown 

 Into the Arterial System by Each Ventricular Systole," Philadelphia Medical Times, 

 Jan. 26, 1884, and "The Time Required by the Blood for Making One Complete Circuit of 

 the Body," Transactions of the College of Physicians, Philadelphia, 1884, and American 

 ' Journal of the Medical Sciences, April, 1884. Also W. H. Howell and F. Donaldson, 

 "Proceedings of the Royal Society," No. 226, 1883 and 1884, p. 139, and Stolnikow, Archiv 

 fur Anat. u. Physiologic, 1886. 



