Pushing boundaries

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Across
  1. 3. reasonable; making use of reason and good sense
  2. 4. poisonous or harmful substances
  3. 6. The state of being fully grown or developed
  4. 8. exact; accurate
Down
  1. 1. Biological growth processes that enable orderly changes in behavior
  2. 2. those who study the brain and the nervous system
  3. 5. the power of knowing things without thinking; sharp insight
  4. 7. held back; restrained