The Expression of the Emotions in Man and Animals Chapter III - General Principles of Expression concluded

In which the intimate workings of the nervous system are observed to produce involuntary bodily expressions independently of the will or habit, manifesting in tremors, altered secretions, and muscular movements under intense emotion or sensation. These direct effects, intertwined with habitual responses and the principle of antithesis, offer a complex yet enlightening framework for understanding the outward signs of pain, rage, joy, and terror across man and animals.