110 ANATOMY FOR NURSES. [CHAP. X. 



the heart sending the pure oxygenated blood to the general 

 system, and the artery from the right side of the heart sending 

 the impure blood to the lungs for purification. The more ex- 

 tensive circulation is usually called the general or systemic 

 circulation, while the lesser circulation is generally known as 

 the pulmonary. 



Some features of the arterial circulation. The flow of blood 

 into the arteries is most distinctly intermittent ; sudden, rapid 

 discharges alternating with relatively long intervals during 

 which the arteries receive no blood from the heart. Every 

 time the heart beats just as much blood flows from the veins 

 into the right auricle as escapes from the left ventricle into the 

 aorta, but this inflow is much slower and takes a longer time 

 than the discharge from the ventricles. 



The pulse. When the finger is placed on an artery a sense 

 of resistance is felt, and this resistance seems to be increased at 

 intervals, corresponding to the heart-beat, the artery at each 

 heart-beat being felt to rise up or expand under the finger. 

 This constitutes the pulse ; and, in certain arteries which lie 

 near the surface, this pulse may be seen with the eye. When 

 the finger is placed on a vein very little resistance is felt ; and, 

 under ordinary circumstances, no pulse can be perceived by the 

 touch or by the eye. 



As each expansion of an artery is produced by a contraction 

 of the heart, the pulse, as felt in any superficial artery, is a 

 convenient guide for ascertaining the character of the heart's 

 action. The radial artery at the wrist, owing to its accessible 

 situation, is usually employed for this purpose. Any variation 

 in the frequency, force, or regularity of the heart's action is 

 indicated by a corresponding modification of the pulse at 

 the wrist. 



The average frequency of the pulse in man is seventy-two 

 beats per minute. This rate may be increased by muscular 

 action. Even the variation of muscular effort entailed between 

 the standing, sitting, and recumbent positions will make a 

 difference in the frequency of the pulse of from eight to ten 

 beats per minute. Age has a marked influence in the same 

 direction. According to Carpenter, the pulse of the foetus is 

 about 140, and that of the newly born infant 130. During the 

 first, second, and third years, it gradually falls to 100 ; by the 



