THE CIRCULATION . 189 



2. Rate of Speed of Pulse. This wave runs at a defin- 

 ite speed along the arteries, which is in man about twenty- 

 five or thirty feet per second. This rate shows that a pulse 

 wave runs out at its peripheral end and is over before the 

 succeeding one is inaugurated. This wave must not be 

 understood as an actual forward movement of the blood, 

 but is a mere pressure wave, just as in the motion of waves 

 on a surface of water, the water itself does not move for- 

 ward with the waves, but moves up and down in almost the 

 same place, as is indicated by observing any floating object 

 which does not travel along with the wave at all. 



3. Kinds of Pulses. An examination of the pulse wave 

 enables the practiced physician to learn much about the 

 state of things in the general circulation. Thus, a phy- 

 sician can distinguish four different kinds of pulses: First, 

 \kzpulsusfrequens, or the pulsus rarus, depending on the 

 number of heart beats per minute. Second, the pulsus 

 celer, or the pulsus tardus, depending on the quickness 

 with which a single beat is t accomplished. It indicates 

 whether in the individual beat of the heart the ventricles 

 contract energetically or slowly. This must not be con- 

 founded with the rate of the pulse or \hz pulsus frequens , for 

 the heart might beat but fifty times a minute, say, a very 

 slow rate, and yet perform each beat with a quick, jerky 

 systole. Third, t\\e pulsus magnus, or the pulsus parvus, 

 depending on the amount of blood which is thrown into the 

 arteries at each beat. A pulsus magmis, or big pulse, 

 would be indicated by the increased size of the artery in 

 question, while a pulsus parvus, or small pulse, would be 

 indicated by a more or less collapsed artery. Fourth, the 

 pulsus durus, or the pulsus mollis, that is, a hard pulse or 

 a soft pulse, depending on the amount of pressure necessary 

 to completely compress an artery, and so prevent the blood 

 from flowing past the point of compression. In other words, 

 the pulse is hard when the pressure of blood is high and 

 vice versa. Here, also, a hard pulse must not be con- 

 founded with a big pulse. Thus it is possible to conceive 



