The Expression of the Emotions in Man and Animals Chapter I - General Principles of Expression Part 2

In which careful observation reveals that many reflex actions and habitual movements, originally acquired for definite purposes through voluntary effort, have become inherited and often persist without usefulness, manifesting as expressions of various sensations and desires. The habits of animals, from the circling of dogs before rest to the pawing of horses eager for food, exemplify how such actions, though sometimes purposeless, retain their ancestral origins and offer insight into the interplay of voluntary and involuntary muscular control.