276 THE CIRCULATION OF THE BLOOD 



1. The beginning of the sphygmic period (E) (line 5). 

 ' 2. The end of the sphygmic period (E) (line 5). 



3. The auricular wave. 



4. The beginning of ventricular systole (difference between 1 and 4 

 equals presphygmic interval). 



5. The opening of auriculoventricular valves (lowest point in tracing). 

 The exact moment at which the heart sounds are heard can usually 



be indicated on the tracing. 



It is important to make certain that the button of the tambour is ac- 

 curately over the apex beat, since otherwise a depressed or negative 

 wave may be inscribed at ventricular systole. 



Simultaneous Arterial Pulse Tracings. The velocity of the transmis- 

 sion of the pulse wave is calculated by measuring the time between the 

 systolic rise in the carotid and in the radial arteries, tracings of which 

 are taken by applying one receiving tambour to the carotid artery and 

 another to the radial artery. 



Abnormal Pulses 



The following is a brief description of the main character of abnormal 

 pulses: 



The Ventricular Pulse. In this no "a" waves are present in the 

 jugular tracing, the heart action being either regular or irregular. In 

 the former case, the absence of the "a" waves may depend on: (1) over- 

 filling of the right auricle, (2) increase in the heart rate, or (3) complete 

 heart-block associated with auricular fibrillation. When the heart is 

 irregular, the absence of the "a" waves signifies auricular fibrillation. 



Delayed Conduction and Heart-block. This causes a change in the 

 time relationship of the "a" and "c" waves in the jugular curve. When 

 the heart-block is of the first degree, the "a-c" interval merely becomes 

 lengthened, but when it is of such degree that the normal impulse some- 

 times fails to be conveyed along the auriculoventricular bundle, isolated 

 "a" waves can be detected. In the higher degrees of heart-block there 

 are regularly recurring "a," waves having no constant time relationship 

 to the "c" waves. For the purpose of exact analysis of the curves in 

 suspected cases of delayed conduction, it is often advantageous to draw 

 vertical lines below the tracing representing the beginning of auricular 

 and ventricular systole. This has been done in the tracing reproduced 

 in Fig. 99. 



The line joining these two verticals indicates the conduction time 

 or "a-c" interval. When it exceeds one-fifth of a second, there is 

 delay in the conduction time. 



