280 Br W. H. Gaskell, On certain points [Nov. 27, 



Stannius ligature, or in either frog or tortoise when the clamp in 

 the auriculo- ventricular groove is suddenly tightened, for such 

 contractions always commence with a quick rate and become 

 slow r er and slower until in a short time they disappear. Again 

 just as we have seen that the spontaneous rhythm is set up 

 quicker the nearer the section is to the sinus, so also is the 

 maximum rate attained more quickly, and the rapidity reached 

 more nearly approaches that of the sinus itself the nearer the 

 section is to the sinus. 



Thus the manifestation of the spontaneous beats of the sinus, 

 of the whole auricle, and of the whole ventricle presents a descend- 

 ing series of phenomena in which the connection between two 

 consecutive links is so close, as to lead to the conclusion that the 

 same cause underlies the rhythmical spontaneity in each case. If 

 then the beats of the sinus and therefore of the heart as a whole 

 are due to motor ganglia, so too are the spontaneous contractions 

 of the isolated ventricle ; if on the other hand, reason is given to 

 ascribe the ventricular beats to a rhythmical property inherent in 

 the ventricular muscle, then it is a fair conclusion to attribute the 

 sinus beats and therefore the heart beat to a similar property of 

 the muscular tissue of the sinus. That the latter of these two 

 views is the correct one the following experiment seems to show. 



Two strips of tissue are cut from the apex of the ventricle in 

 the same direction, of the same length and are in every respect as 

 similar as possible to each other ; these two pieces are then sus- 

 pended in two moist chambers and their movements registered by 

 a lever attached to the free end of each strip by means of a thread. 

 The one preparation is left entirely alone, the other is stimulated 

 every ten seconds by single induction shocks applied at the fixed 

 end, and at intervals a weak interrupted current is sent through 

 the whole strip by means of two thin wire electrodes which are so 

 fine and light as not in any way to hinder the movements of the 

 muscle. 



It is then found that after about an hour and a half or slightly 

 longer the single induction shocks are no longer required in order 

 to induce rhythmical contractions of the strip of muscle, for the 

 strip is now contracting of itself with increasing regularity of 

 rhythm and with strong vigorous contractions, w r hile the control 

 strip which has been left alone still remains absolutely quiescent. 

 The effect then of the single induction shocks combined with the 

 weak interrupted current has been to bring the muscular strip 

 into such a condition of instability that rhythmical discharges take 

 ■place in it, so causing rhythmical contractions. These rhythmical 

 beats are clearly not simply the after effect of the previous 

 stimulations in the same w r ay, as a stimulus applied to the base 

 of the frog's ventricle produces not a single beat but a series 



