

THE EVENTS OF THE HUMAN CARDIAC CYCLE 87 



In animals curves have been secured from the vein wall 

 or blood stream, by Gottwalt, Fra^ois-Franck, Morrow ( 37 ), 

 Fredericq ( 12c ), Rautenberg ( 42c ), and others. The results in man 

 and animals are in such general agreement that one description 

 of them will suffice. 



Speaking broadly, the venous pulse, like the auricular curve, 

 shows three main elevations and three main depressions ; l the 

 general outlines of venous and auricular curves are such as to 

 leave no reasonable doubt that the factors ultimately concerned 

 in the production of their waves are identical for each, a relation 

 on which many writers have laid emphasis. The final evidence 

 depends on the detailed analysis of each wave of the curves and 

 will be undertaken subsequently. For the time being it will be 

 convenient to recognise the three main elevations of the venous 

 curve (the " a," " c," and " v " waves of Mackenzie) as corre- 

 sponding to the three positive waves of the auricular pressure curve, 

 and the three main dips of the venous tracing (the " x," " x'," 

 and " y " depressions of Mackenzie) as corresponding to the three 

 chief negative waves of the auricle. These events are represented 

 in the accompanying figure (Fig. 1), and their relations may be 

 tabulated as follows : 



a " First positive wave. 



x " First negative wave. 



c " Second positive wave. 



x' " . . . . -* . Second negative wave, 



v " . . . . .Third positive wave, 



y " Third negative wave. 



The waves of the jugular pulse have not received such an 

 accurate comparison to standard movements as have the auricular 

 pressures in animals. This is but natural, for with the indirect 

 methods available the sources of error are comparatively large, 

 and little advantage is to be gained by the use of more rapidly 

 travelling recording surfaces. But writers are in the habit of 

 expressing themselves dogmatically as to the time instants at 

 which certain events are taking place, while at the same time 

 they appear to lack a due appreciation of the comparatively rough 

 methods by which the standard movements of the cardiac cycle 

 are fixed in man. Cardiographic curves are notoriously uncertain, 



1 A record of the venous pulse is shown in Fig. 3, at the end of thU article. 



