1. The alkaloids (curare, atropine, and nicotine) in molluscs and arthropods stimulate and paralyze the central nervous system and peripheral (visceral) ganglia, but do not paralyze the motor nerve endings to skeletal or visceral muscle.
2. They stimulate and paralyze the denervated heart.
3. They paralyze or block the cardioinhibitory nerves, but not the cardioaccelerator nerves.
4. In the Limulus heart these drugs act primarily on the heart ganglion, not on the heart muscle or the intrinsic motor nerve fibers.