410 



Messrs. Sanderson and Page 



[May 23, 



II. " Experimental Results relating to the Rhythmical and Ex- 

 citatory Motions of the Ventricle of the Heart of the Frog, 

 and of the Electrical Phenomena which accompany them." 

 By J.Burdon Sanderson, M.D., LLD., F.R.S., and F. J. M. 

 Page, B.Sc, F.C.S. Received May 6, 1878. 



The results which are shortly stated in the following paragraphs 

 relate to (1) the order and duration of the rhythmical and excitatory 

 motions of the heart of the frog ; (2) the normal electrical condition 

 of the surface of the heart and the influence thereon of mechanical, 

 chemical, and thermal injuries ; and (3) the characters of the normal 

 and of the excitatory electrical variation, and the modifications of 

 those characters which are induced by injuries of the surface, and 

 under the temporary influence of radiant heat. 



Section I. — Order and Duration of the Motions of the Heart. 



1. Duration of the Ventricular Systole.- — In the rhythmically contract- 

 ing excised heart, i.e., in the heart removed by cutting across the sinus, 

 which will in this paper be called "the entire heart," the frequency of 

 the contractions is usually, in winter frogs, a little over 30 per minute. 

 The systole of the ventricle lasts about one second. The contraction 

 attains its maximum in a little more than half a second after its 

 commencement, declining at first gradually, afterwards more suddenly. 

 The sadden relaxation occurs between 0"'7 and 0"'9 after the com- 

 mencement. At the close of this period the ventricle does not become 

 entirely flaccid, for a lever resting upon it continues to descend for 

 about a third of a second. 



In the rhythmically contracting heart, removed by cutting through 

 the auricles, to be called hereafter " the ventricle preparation," the 

 duration of the ventricular systole is about 1"*35. It attains its maxi- 

 mum at 0"'8 after its commencement, and relaxes rapidly between 

 1"-1 and 1"3. 



In these statements the word commencement is understood to mean 

 the beginning of the hardening of the ventricle. It is preceded by a 

 period of partial contraction of which the duration is about 0"'15, and 

 which we propose to call the period of prse- contraction. 



2. Relation between the Periods of Contraction of the Auricles and Ven- 

 tricles. — In the entire heart, contracting rhythmically, the contraction 

 of the auricle begins about 1"'4 before that of the ventricle, and the 

 maximum of the auricular systole is attained 1"*2 before that of the 

 ventricle. There is an interval of not less than half a second between 

 the end of the auricular contraction as indicated by the movement of 

 a light lever resting upon it and the beginning of that of the ventricle. 

 It follows from this statement that when the heart is acting at its 

 normal frequency, the beginning of the auricular contraction nearly 



