THE EVENTS OF THE HUMAN CARDIAC CYCLE 101 



no outward resemblance to the waves of the pure carotid pulse. 

 Briefly, in such cases it must be assumed that the primary wave 

 is alone transmitted, an assumption which it is difficult to make. 

 It may be asked why, if the primary wave is recorded, the 

 dicrotic should not also leave its impression on the tracing. Again, 

 it requires as a rule a firmer pressure to bring out a maximum 

 arterial tracing than it requires for the venous. Venous tracings 

 of the greatest amplitude are often to be obtained by the lightest 

 application compatible with closure of the mouth of the receiver. 

 We have further seen that the synchronicity of the " c '' wave 

 and the carotid shock has not been fully established (Bard and 

 Bachmann). The tracings given to show simultaneous onset often 

 show a slight deviation, which may of course be explained by a 

 difference in level at which they were obtained and to a slight 

 transmission delay. The argument that the " c " wave is absent 

 from the liver pulse is the strongest of those brought in favour 

 of its arterial origin, and has not yet met with a satisfactory 

 explanation. The liver tracings are of a very complex nature, 

 combining expansile pulsation with up and down movements of 

 the whole organ. Rautenberg ( 42c ) has given a tracing in which 

 the " c " wave appears to be present, but it is possible that in 

 this instance insufficient care was employed to avoid the trans- 

 mitted shock from the aorta. The author is of opinion that the 

 " c " wave is occasionally visible in the veins of the neck. 



Finally, it cannot be affirmed at present that the " c " uxtve is 

 purely arterial or purely venous in origin, and while it cannot be 

 denied that both factors may be contributory under certain conditions, 

 it is highly probable that in one case the arterial and in another the 

 venous element will predominate. 



As to whether there is a transmitted shock from the aorta or its 

 branches direct to the veins, there is little evidence beyond that 

 already examined. Fredericq points out that, as the rate of trans- 

 mission is dissimilar in artery and vein, the view is incompatible 

 with the opinion that the waves appear together in the neck. 

 Morrow uses, as an argument against such transmission, the fact 

 that the " c " wave is frequently absent from the femoral venous 

 curve, though the venous channel which connects the femoral vein 

 to the heart is throughout in close contact with pulsating arteries. 1 



1 The question has been recently discussed more fully by the author (Brit. Afed. 

 Journ., Nov. 1905). 



