THE CIRCULATION OF THE BLOOD. 283 



well as by a return of the auriculo-ventricular septum to its normal position, 

 the result of a relaxation of the papillary muscles at a time when the intra- 

 ventricular pressure is still higher than the intra-auricular pressure. It 

 amounts to about 5 mm. of Hg. 



The third negative wave, vf, appears very shortly after the relaxation of 

 the ventricle and though there is at this moment a rapid fall of intra- 

 ventricular pressure, on opening of the auriculo-ventricular valves and a 

 descent of blood into the ventricle, the fall of auricular pressure seldom 

 amounts to more than 0.5 mm. of Hg. 



A Graphic Record of the Auricular and Ventricular Contractions 

 of the Human Heart. From the similarity of the anatomic arrangement 

 of the human heart to that of mammals in general it is permissible to assume 

 that a graphic record of the auricular and ventricular contractions of the 

 human heart would resemble in its general 

 features that of the hearts of mammals hereto- 

 fore experimented on, and that the same series 

 of events present themselves in the human heart 

 during each cycle, though by reason of the 

 difference in the rate of the beat, the duration 

 of each event in the cycle is somewhat different. 



The nearest approach to obtaining a graphic 

 record of the auricular and ventricular con- 

 tractions of the human heart by the direct ap- 

 plication of exploratory tambours was made by 



Francois Frank on a woman whose heart was FIG. 132. TRACINGS OF 

 congenitallydisplaced into the abdominal cavity. 

 An investigation revealed the fact that this WITH ECTOPIA OF THE HEART, a, 

 woman had a large opening in the anterior Auricular; v, ventricular. (Fran- 

 portion of the diaphragm through which the f 



ventricle had passed and formed a large protrusion in the epigastric 

 region. Through thin and relaxed abdominal walls the ventricular pul- 

 sations could be distinctly felt as well as the pulsation of what ap- 

 peared to be the inferior portion of the right auricle. A fibrous ring 

 around the edge of the opening in the diaphragm supported the heart 

 at the auriculo-ventricular groove. On the application of exploratory 

 tambours in connection with recording tambours one to the right 

 ventricle, the other to the right auricle, the record shown in Fig. 132 was 

 obtained of which the upper line represents the contraction of the auricle 

 and the lower line the contraction of the ventricle. A comparison of the 

 record with that obtained from the horse, Fig. 125, p. 273, shows that the 

 relation of the auricular to the ventricular systole is the same in the former 

 as in the latter and that in their general features the two records correspond, 

 from which it may be inferred that in the human heart the events occurring 

 during the cycle are practically identical with those occurring in the hearts 

 of other mammals. The small size of the auricular curve and the absence of 

 undulations are probably due to the fact that the tambour was placed on 

 only a portion of the auricle. 



A Schematic Representation of the Events of a Cardiac Cycle in 

 Man. From graphic studies of the cardiac impulse, of the pressure changes 



