THE ACTION OF CERTAIN DRUGS ON THE INSECT CENTRAL NERVOUS SYSTEM

¹ TUFTS COLLEGE, MASSACHUSETTS

1. Adult praying mantids and cockroaches were injected in the head with solutions of various drugs, and the changes in general reflex activity were recorded.

2. Strychnine caused a decrease in reflex activity in both insects, large doses causing complete cessation of antennal and mouth-part movement. This is contrary to its effect on the vertebrate spinal cord.

3. Pilocarpin and eserine bring about an increase in mouth-part and antennal movement, head movement and extensor leg tonus, and produce spasmodic twitching and general contraction of the body musculature. In the case of pilocarpin this effect is prevented by atropin.

4. Acetylcholine alone has no detectable effect on activity. Its effect, if any, when injected with eserine is masked by the excitatory effect of eserine.

5. It is concluded that, in their reactions to drugs, the nervous systems of the two insects studied show little similarity to the vertebrate central nervous system, but considerable similarity to the vertebrate parasympathetic.

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