Recoil Curves as shown by the Hot- Wire Microphone. 293 



interpretation of the two peaks (2 and 3) is, we think, as follows : The first is 

 probably due to the movement of the body headwards as the mass of blood 



FIG. 7. (Read left to right) 



passes down the aorta, while the second is caused by the return 'of the 

 displaced body to normal. 



The interpretation of the two smaller peaks (4 and 5) is, however, not easy, 

 as it is difficult to believe that a recoil of this magnitude can be produced 

 entirely by auricular systole. 



In this connection, it should not be forgotten that patient's with large and 

 heavy hearts, not necessarily dilated post-mortem, frequently shake the whole 

 bed. The question, therefore, arises whether, or not, some of the features of 

 the recoil curve are due to the actual movement of the heart itself. It lias 

 been shown by needles passed into the base centre and apex that the base 

 moves downward during systole. The elastic recoil of the distended aorta 

 also requires taking into consideration. These questions have been left for 

 subsequent investigation. 



