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Messrs. D. H. de Souza and J. A. Hewitt. 



attached to the cannula, was excised and perfused by Symes's method, with 

 Einger's fluid (NaCl 0-6 per cent., KCl 0-026 per cent., CaCla + GHaO 

 0'032 per cent.), at a pressure of about 4 cm. of water, and a tracing of 

 the beats was taken by means of a lever, connected by a hook to the tip 

 of the ventricle, and writing on the smoked surface of a revolving drum. 

 Shortly after the perfusion was begun, the heart beats were normal and 

 regular. As soon as it was evident that this normal regularity was 

 established, the perfusion fluid was replaced by Einger's fluid, containing 

 i-inositol (1 in 750). In less than a minute after the inositol solution 

 reached the heart, the beats showed periodic grouping. The heart was 

 perfused with the inositol solution for 13 minutes, then with ordinary 

 Einger's solution for half-an-hour, and during the whole time grouping 

 continued. After this the perfusion was ended by the solution's running 

 out. Grouping ceased, and the heart beat regularly, the beats gradually 

 diminishing in force and frequency. At this stage the experiment was 

 concluded. 



Interpretation of the Tracing. — Fig. 1, taken from a part of the tracing, 

 is a type of the whole. It shows the ventricle beats arranged in groups, 

 with pauses between the groups. The auricle beats are clearly seen and 

 continue to occur at regular intervals during the ventricular pauses. 

 Dr. I.ocke, who happened to be present while the experiment .was in 

 progress, drew our attention to the fact that, in the groups, the ventricle 

 beats did not seem to bear a definite time relationship to the auricle beats. 

 This is evident in the tracing, where, during the grouping, the contraction 

 of the ventricle occurs at a variable time after that of the auricle, and may even 

 synchronise with it. We have carefully measured aiid analysed this tracing, 

 and we submit in fig. 2 a diagram which illustrates the essential points. 



The vertical lines in the upper half of the diagram indicate the relative 

 positions of the contractions of the auricles, those in the lower half the 

 relative positions of the contractions of the ventricle during the same period 

 of time. The intervals between the auricle contractions are practically 

 equal ; accordingly, when the auricle beats are obscured on the tracing by 

 ventricle beats, we have inserted broken lines at this interval from the 

 lines preceding and following them. Two ventricular pauses are shown, 

 and a complete group between them. 



It is evident that there is no definite time relationship between the 

 contractions of the auricles and of the ventricle in this group, such as can 

 be explained by a condition of partial heart block, and this is the same 

 for all the groups ; in fact, it is obvious that, during a part of the time,, 

 the ventricle was beating more frequently than the auricles. 



