Scientific Proceedings (76). 



atrioventricular funnel of Malacoclemmys geographica are the 

 portions which are most efficient in conducting the contracting 

 impulse from the auricles to the ventricle. When the auricles 

 are partially separated from the ventricle by a series of cuts 

 leaving only a narrow connection, and in consequence of which 

 atrio-ventricular block (complete or incomplete) has been brought 

 about, it is these parts which are later most capable of conducting 

 the impulse from the auricles to the ventricle so that the contrac- 

 tions of the latter follow those of the auricle coordinatedly, or so 

 that the incomplete block is decreased. 



Stimulating the funnel of beating (in situ and excised) and still 

 hearts (first Stannius ligature) with single shocks (quick make 

 and break) and with interrupted currents of short duration 

 have shown (1) that the funnel is more easily excited than the 

 base of the ventricle, (2) that the right and left parts of the funnel 

 are more easily excited than other parts (dorsal and ventral) and 

 (3) that the excitability of the funnel increases as one approaches 

 the auricle. 



The stimulation of the funnel just below the level of the A-V 

 boundary of beating hearts with interrupted currents, even when 

 these are strong and of long duration, can only occasionally pro- 

 duce a "fibrillation" of the ventricle or a V-A rhythm (funnel 

 rhythm) which lasts over after the stimulation is discontinued. 

 This is possible, however, and curves have been obtained from 

 excised hearts showing a duration for several seconds of a funnel 

 rhythm following a ventricular "fibrillation." In the still heart 

 the setting up of a funnel rhythm is more easily and frequently 

 accomplished, and several cases have been registered showing 

 a funnel rhythm lasting for several minutes. 



104 (1168) 



The influence of the vagi and of the sympathetic nerves on the 

 rhythm-forming power of the atrioventricular con- 

 nection in the turtle. 



By Henry Laurens and C. C. Gault. 



[From the Osbom Zoological Laboratory , Yale University.] 

 The investigations here reported were undertaken to deter- 

 mine the action of the vagus and sympathetic nerves upon the 



