Investigations initiated some 30 years ago revealed the existence in insects of factors acting on the contractility of the visceral muscles. The earliest work of Koller (1948) showed that head and brain extracts of different species induced the acceleration of contractions of the Malpighian tubules (Fig. 42). Subsequent investigations dealt with the heart, Malpighian tubules, gut, and oviducts, and were almost always carried out in vitro. Most of them dealt with the heartbeat of the cockroach Periplaneta americana. The active factors were discovered in the corpora cardiaca and the central nervous system, and in the effectors themselves (Fig. 43).
KeywordsVentral Nerve Cord Malpighian Tubule Stick Insect Abdominal Ganglion Lateral Nerve
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