A systematic account of experiments examining physiological changes that accompany pain, hunger, fear, and rage. It explains autonomic nervous system organization and shows how emotional excitation alters digestion, circulation, respiration, coagulation, and glandular secretion. Experimental evidence links splanchnic nerve activity and adrenal secretion to rapid increases in blood pressure, mobilization of energy, inhibition of intestinal motility, and accelerated clotting; hunger sensations and gastric contractions are described alongside methods used to record them. The work argues that these coordinated visceral reactions are adaptive responses to threat or need and provides detailed experimental procedures and results supporting a functional interpretation of emotional bodily changes.