For a deeper look at Braid's medical career and his "crucial experiment," see the academic overview on ResearchGate .
“I regard this book as THE fountain head of hypnosis. Braid not only gives us the word we now use for our subject, but brought to it a clarity of thought and an energy of experimentation which is unparallelled.” Ragged University NEURYPNOLOGY James Braid
Initially, Braid believed the state was caused by physical fatigue of the eyes and nervous system from fixed staring. For a deeper look at Braid's medical career
You can find the full original text or detailed historical summaries through these sources: NEURYPNOLOGY James Braid