144 THE PULSE-CURVES OF VARIOUS ARTERIES. 



between the pulse-beats, or it may be very soft, as in insufficiency of the aortic 

 valves. In this case, after the systole of the left ventricle, owing to the incom- 

 petency of the semi-lunar valves, a large amount of blood flows back into the 

 ventricle, so that the arteries are thereby suddenly rendered partially empty. [The 

 sudden collapse of the artery gives rise to the characteristic "pulse of unfilled 

 arteries. "] 



Under similar conditions, the volume of the pulse is obvious from the size of 

 the sphygmogram, so that we speak of a large and a small pulse (P. magnus and 

 parvus). Sometimes the pulse is so thready and of such diminished volume that 

 it can scarcely be felt. A large pulse occurs in disease when, owing to hyper- 

 trophy of the left ventricle, a large amount of blood is forced into the aorta. A 

 small pulse occurs under the opposite condition, when a small amount of blood is 

 forced into the aorta, either from a diminution of the total amount of the blood, 

 or from the aortic orifice being narrowed, or from disease of the mitral valve ; again, 

 where the ventricle contracts feebly, the pulse becomes small and thready. 

 Sometimes the pulse differs on the two sides, or it may be absent on one side. 



Waldenburg constructed a "pulse-clock " to register the tension, the diameter 

 of the artery, and the volume of the pulse upon a dial. It does not give a graphic 

 tracing, the results being marked by the position of an indicator. 



72. The Pulse-Curves of Various Arteries. 



1. Carotid (Fig. 54, A.; Fig. 58, 1, II, III ; Fig. 64, C and C,). 



The ascending part is very steep the apex of the curve (Fig. 58,P) 

 is sharp and high. Below the apex there is a small notch the 

 "AORTIC NOTCH" (Fig. 58, K) which depends on a positive wave 

 formed in the root of the aorta, owing to the closure of the aortic 

 valves, and propagated with almost wholly undiminished energy 

 into the carotid artery. Quite close to this notch, if the curve be 

 obtained with minimal friction, the first elastic vibration occurs (Fig. 

 58, 11,0). Above the middle of the descending part of the curve is the 

 dicrotic elevation, E, produced by the reflection of a positive wave 

 from the already closed semi-lunar valves. The dicrotic wave is rela- 

 tively small on account of the high tension in the carotid artery. 

 After this the curve falls rapidly, but in its lowest third two small 

 elevations may be seen. Of these the former is due to elastic vibration. 

 The latter represents a second dicrotic wave (Fig. 58, III, R), (Landois, 

 Moens). Here there is a true tricrotism, which is more easily obtained 

 from the carotid on account of the shortness of the arterial channel. 



Moens describes the "aortic elevation" as occurring at the moment of the 

 closure of the aortic valves. 



2. Axillary Artery (Fig. 58, IV). 

 



In this curve the ascent is very steep, while in the descent near the 

 apex there is a small (aortic) elevation, K, caused by a positive wave, 

 produced by the closure of the aortic valves. Below the middle there 



