972 PHYSIOLOGY 



becomes very marked. Under such circumstances it may be easily felt 

 with the finger at the wrist, and in many cases the mistake has been com- 

 mitted of taking the dicrotic wave for a normal beat, and so doubling the 

 rate of the pulse. There can be little doubt that, in the production of such 

 a marked dicrotism, reflection from the periphery plays an important part. 

 With a high blood pressure and rigid arteries, a reflected wave will travel 

 back very quickly and will tend to add itself to the primary wave. With 

 a low blood pressure, dilated arteries, and the output of the heart thrown 

 rapidly into a relatively empty arterial system, the primary wave will 

 rise and fall very rapidly and the reflected wave will travel back along the 

 arteries more slowly, so that its main effect will be to add to the dicrotic 

 elevation normally proceeding outwards from the heart towards the peri- 

 phery. The figure 420 VI represents the condition as it is found in the 

 femoral artery under normal circumstances, when the reflected wave addvS 

 to the height of the primary wave. In 420 V the reflected wave ' a ' 

 would tend to add to any dicrotic elevation present at this point, and prob- 

 ably represents the relation existing in the arterial system with relaxed 

 arteries and a heart beating forcibly but throwing out only a small amount 

 of blood at each beat. 



From time immemorial the physician has sought by feeling the pulse 

 to come to some idea as to the condition of the circulation. A number of 

 different qualities have therefore been distinguished. According to the 

 number of beats per minute the pulse is designated as frequent or rare. 

 The size of the pulse has reference to the amplitude of excursions of each 

 beat and the pulse is distinguished as large or small. The velocity of the 

 pulse expresses the speed with which the excursion is accomplished. The 

 quick pulse is one in which the artery presses against the finger suddenly 

 and then disappears suddenly, while in the slow pulse the period during 

 which, pressure can be felt is more prolonged. The hardness of the pulse 

 is determined chiefly by the blood pressure. If the pulse is compressible 

 it is spoken of as soft', if it can only be obliterated with difficulty it is hard. 

 Certain combinations of these qualities are also described. Thus a large 

 and hard pulse is spoken of as strong, a weak pulse being both small and soft. 

 A small hard pulse is called contracted. If the rhythm of the heart beat 

 is irregular the pulse is also irregular. An ntlfnvidn,! pulse is one in which 

 one heart beat is dropped occasionally, /. c. once, in every four or eiuht heats, 

 and may be due to the interposition of a ventricular contraction which is 

 too weak 1n send the pulse alon-: so far as the radial artery. 



Judgments as to the conditions of the heart and circulation from the 

 feeling of the pulse oscillations must however be n.ade with extreme 

 caution. The pulse curve may indeed ^ive approximate information as 

 to the condition both of the heart and the arterial system. Thus the period 

 between the bei/nmin^ of the primary elevation and the dicrotio notch 

 Corresponds to (he outflow <> blood from ventricle to aorta. A larsre pulse 

 curve does not necessarily indicate a bi^ output, since, the expansion of the 

 artery is determined not only by events occurring in the aorta but also by 



