1880.] Experimental Researches : Heart of the Frog. 381 



Two parallel series of results are obtained, which when set off as 

 ordinates on the same time-axis exhibit the characters shown in the 

 figure. Our results show that in a fresh preparation at 12°, the 

 excitatory wave is propagated at a rate of about 130 millims. per 

 second. It will be noticed that the rapidity with which the electromo- 

 tive force of the initial phase attains its maximum, renders it possible 

 to make this observation with great exactitude. 



Fig. 2. 



The figures above the line denote degrees of the scale of the rheotome ; those 

 below, lOOths of a second measured from the moment of excitation ; those in the 

 vertical column degrees of the scale of the galvanometer. The ascending line to the 

 left shows the deflections observed when the galvanometer circuit was opened at 

 38, 40, 42, and so on of the scale of the rheotome, the preparation being led off at 

 m and/. The similar line to the right shows the corresponding deflections at 50, 52,. 

 and so on, when m' was substituted for m and the excitation wave had 4 millims. 

 further to go. The records represent the means of two observations taken as soon 

 as possible after each other. It is reckoned that in these instances the 4 millims. 

 were accomplished in the time corresponding to 11 divisions of the rheotome scale, 

 i.e., in 0-032 second. 



The facts which have been stated in the preceding paragraphs are 

 consistent with the following theories : — 



1. Every excited part is negative to every unexcited part, so long as 

 the state of excitation lasts. 2. The local duration (ortliche Bauer,. 

 Engelmann) of the excitatory state, i.e., the time it lasts in each 

 structural element, is measured by the time-interval between the begin- 

 ning of the initial and the beginning of the terminal phase of the 

 variation. 



As regards the second of these propositions, we are in dis- 

 agreement with Professor Engelmann, who attributes to the excita- 

 tory process in the ventricle of the frog's heart a duration of 

 only two-tenths of a second. We conclude, from our own observa- 

 tions, that its duration is nearly two seconds at the temperature at 



