THE EVENTS OF THE HUMAN CARDIAC CYCLE 91 



fundamental and constant, or at present of any great practical 

 significance. It v.-ould be premature and unprofitable to discuss 

 them. 



(c) The Evidence obtained from Intra-cesophageal Trac- 

 ings. By means of an cesophageal bougie, fitted with a small elastic 

 balloon, tracings have been obtained from the heart, which are 

 not without value. The auricular curves are from the left auricle, 

 which lies in contact with the gullet. They are to be used -with 

 caution, for they suffer in a measure from the same defect as do 

 cardiographic curves ; it is not possible to say to what extent 

 they are volume and to what extent pressure curves. Moreover 

 they show considerable variation according to the level at which 

 the balloon is placed (Young and Hewlett 50 ). In dogs such 

 tracings were obtained as early as 1888 by Fredericq, and recently 

 Minkowski ( M ), Rautenberg ( 4 ' 2a " c ), Joachim ( 27 ), Young and Hewlett, 

 and others have secured them in man. The tracings are in the 

 main in fair agreement, and show curves similar to those of 

 intra-auricular pressure in animals. Disagreement, however, has 

 arisen over that portion of the curve representing auricular 

 contraction. 



According to the earlier observations, auricular contraction is 

 indicated by a depression in the tracing, whereas Rautenberg ( 42a ), 

 in all tracings but one (Fig. 5), attributes a convexity to the same 

 event. 



Now cardiographic curves from the ventricles, when taken 

 from any other point than the apex of the left ventricle, show a 

 curve which is roughly an inverted picture of the intra-ventricular 

 pressure. In one respect the picture shows no inversion, the 

 auricular wave when present retains its intra-ventricular form. 

 Briefly, those portions of the curve are inverted which are de- 

 pendent on active movements of the ventricular wall. In tne 

 same way it would be expected that when intra-auricular and 

 cesophageal curves were compared, those portions of the ceso- 

 phageal curve would show inversion, which were independent of 

 ventricular movements. The curves as interpreted by Fredericq, 

 Joachim, and Minkowski fulfil this expectation ; Rautenberg, on 

 the other hand, finds as a rule no inversion of any part of the curve. 

 As Hering states, it is difficult to understand how a contracting 

 left auricle can raise the cesophageal pressure, at a point at which 



