1. Addition of a homogenate of corpora cardiaca to the fluid bathing an isolated hind gut of Periplaneta produces an increase in tonus, amplitude, frequency and co-ordination of contractions.

  2. The corpus cardiacum acts by stimulating cells in the upper colon to release an indolalkylamine.

  3. This amine acts on the mucles through a peripheral nervous system which can function in isolation from the central nervous system.

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