THE CIRCULATION OP THE BLOOD. 239 



VARIATIONS IN THE CARDIAC PULSATION. 



These may be ascertained either by the investigation of the 

 arteries or of the heart, for every considerable alteration in the 

 working of the heart expresses itself also through the arterial 

 system. In speaking of the pulse, the reference is principally 

 to the arteries, but in. each case we may equally well think of 

 the heart primarily as acting upon the arteries. 



1. The frequency of the heart-beat varies, as might be sup- 

 posed, with a great multitude of conditions, the principal of 

 which are : age, being most frequent at birth, gradually slow- 

 ing to old age, while in feeble old age the heart-beat may, like 

 many other of the functions of the body, approximate the con- 

 dition at birth, being very frequent, small, feeble, and easily 

 disturbed in its rhythm ; sex, the cardiac beat being more fre- 

 quent ia females ; posture, most rapid in the standing position, 

 slower when sitting, and slowest in the recumbent attitude; 

 season, more frequent in summer ; period of the day, more 

 frequent in the afternoon and evening. Elevation of tem- 

 perature, the inspiratory act, emotions, and mental activity, 

 eating, muscular exercige, etc., render the -heart-beats more 

 frequent. 



2. The length of the systole, though variable, is more con- 

 stant than that of the diastole. 



S. The force of the pulsation varies very greatly and exer- 

 cises an important influence on the blood-pressure and the 

 velocity of the blood-stream. As a rule, when the heart beats 

 rapidly, especially for any considerable length of time, the 

 force of the individual pulsations is diminished. 



4. The heart-beat may vary much and in ways it is quite 

 possible to estimate, either directly by the hand placed over the 

 organ on the chest, by the modifications of the cardiac sounds, 

 or by the use of instruments. It is wonderful how much in- 

 formation may be conveyed, without the employment of any 

 instruments, through palpation and auscultation, to one who 

 has long investigated the heart and the arteries with an intelli- 

 gent, inquiring mind; and we strongly recommend the student 

 to commence personal observations early and to maintain them 

 persistently. 



Practitioners recognize the pulse (and heart) as " slow " as dis- 

 tinguished from "infrequent," "slapping," ".heaving," "thrill- 

 ing," " bounding," etc. 



