566 ACTION OF CURAEE, ATROPINE, AND NICOTINE 



3. The Effects of Curare, Atropine, and Nicotine on the Cardioregula- 

 tive Nervous Mechanism. 



Curare, atropine,and nicotine do not paralyze the cardioaccelera- 

 tor nerves in the gasteropod molluscs or the intrinsic motor nerves in 

 the heart of Limulus. The following experiment on Ariolimax may be 

 quoted as typical. 



Apr. 4, 1904. Heart of Ariolimax. 



9.35 a.m. Heart exposed; stimulation of visceral nerve eflf active. Heart 

 bathed in a 0.5 per cent curare solution in plasma; acceleration. 



9.45 a.m. Stimulation of visceral nerve effective. Curare continued. 



10 a.m. Stimulation of visceral nerve effective. Curare continued. 



10.25 a.m. Stimulation of visceral nerve effective. Curare continued. 



10.45 a.m. Accelerator action of nerve partly impaired. Curare solution 

 replaced by blood. 



11.10 a.m. Stimulation of visceral nerve accelerates heart. 



11.30 a.m. Stimulation of visceral nerve accelerates heart. Blood replaced 

 by 0.5 per cent curare solution. Acceleration of rhythm. 



11.50 a.m. Stimulation of visceral nerve has only a very slight action on heart. 

 Rhythm very feeble and slow. 



12.15 p.m. Stimulation of visceral nerve still accelerates heart. Curare 

 solution replaced by blood. 



1.30 p.m. Heart quiescent. Stimulation of visceral nerve (interrupted cur- 

 rent) produced a series of beats in ventricle. 



The diminution of the influence of the motor nerves on the heart 

 after prolonged action of these drugs is evidently due to diminished 

 excitability of the heart. The final failure of the accelerator nerves 

 appears only after such a prolonged action of the alkaloids on the heart 

 that the rhythm is almost, if not entirely, abolished. In Ariolimax it 

 is possible to produce a series of contractions in the ventricle brought 

 to a standstill by curare, atropine, or nicotine on stimulation of the 

 visceral nerve with the tetanizing current. 



I am not in a position to say whether these alkaloids paralyze the 

 accelerator nerves that connect the heart of Limulus with the central 

 nervous system, but neither curare, atropine, nor nicotine abolishes 

 the action of the nerve fibers that pass from the nerve cord on the 

 dorsal side of the heart to the heart muscle. 



Continued Action of Solutions of Curare, Atropine, or Nicotine on 

 the Heart Abolishes the Influence of the Inhibitory Nerves on the Heart 



