352 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION I 



FIG. 33. A: schematic drawing of the "compass-electrode," placed on the epicardial surface of a 

 dog's heart. Two amplifiers are connected in the manner indicated. Various connections may be 

 made by the use of a gang switch. If the records are obtained from connections parallel to the muscle 

 fibers, the potentials and the peak-to-peak distance will reach a maximum, as in the record below. 

 The excitation velocity v may be calculated from the symbols given. [From Schaefer (407).] B: 

 original record made with the electrodes illustrated in A. For convenience the two action potentials 

 are recorded with opposite polarity. Cathode-ray oscilloscope. [From Schaefer (407).] 



FIG. 34. Map of the direction 

 of surface excitation. A. one 

 experiment on the posterior 

 surface of a dog's heart, with 

 the technique of fig. 33 (Experi- 

 ment of Trautwein). B: the 

 results of several experiments on 

 the anterior surface of a dog's 

 heart. [From Schaefer & Traut- 

 wein (412).] 







high apparent velocities would be calculated from 

 .such latencies and the distances at the surface. Since 

 the muscular propagation velocity is relatively slow, 

 a synchronizing mechanism apparently exists, which 

 leads the excitation wave on a more direct route to 

 the various parts of the ventricles. This mechanism is 

 assumed, of course, to function through the Pin^kinje 

 system, but there is no exact proof of this assumption. 

 Figure 35 gives an idea of the spreading process, 

 which indeed seems to imitate the propagation of an 



ink spot on a blotting paper, as Lewis previously 

 stated in reference to the atria. 



In spite of the extreme importance of such measure- 

 ments, nobodv has ever tried to measure the propaga- 

 tion process in the human lieart bv a reliable method. 

 There have been some ol)servations made with uni- 

 polar recordings, evaluating the intrinsic deflection 

 (95), but the results deviate greatly from those 

 obtained from the dog's heart, insofar as the earliest 

 excitation wave recorded appeared near the base of 



