The simplest actions in which the nervous system is concerned are what we call reflex actions.  All the visceral actions which keep us alive from moment to moment, the movements of the heart and lungs, the contractions of arteries, the secretions of glands, the digestive operations of the stomach and liver, belong to the class of reflex actions.  Throughout the animal world these acts are repeated, with little or no variation, from birth until death, and the tendency to perform them is completely organized in the nervous system before birth.  Every animal breathes and digests as well at the beginning of his life as he ever does.  Contact with air and food is all that is needed, and there is nothing to be learned.  These actions, though they are performed by the nervous system, we do not class as psychical, because they are nearly or quite unattended by consciousness.  The psychical life of the lowest animals consists of a few simple acts directed toward the securing of food and the avoidance of danger, and these acts we are in the habit of classing as instinctive.  They are so simple, so few, and so often repeated, that the tendency to perform them is completely organized in the nervous system before birth.  The animal takes care of himself as soon as he begins to live.  He has nothing to learn, and his career is a simple repetition of the careers of countless ancestors.  With him heredity is everything, and his individual experience is next to nothing.

As we ascend the animal scale till we come to the higher birds and mammals, we find a very interesting and remarkable change beginning.  The general increase of intelligence involves an increasing variety and complication of experiences.  The acts which the animal performs in the course of its life become far more numerous, far more various, and far more complex.  They are therefore severally repeated with less frequency in the lifetime of each individual.  Consequently the tendency to perform them is not completely organized in the nervous system of the offspring before birth.  The short period of ante-natal existence does not afford time enough for the organization of so many and such complex habitudes and capacities.  The process which in the lower animals is completed before birth is in the higher animals left to be completed after birth.  When the creature begins its life it is not completely organized.  Instead of the power of doing all the things which its parents did, it starts with the power of doing only some few of them; for the rest it has only latent capacities which need to be brought out by its individual experience after birth.  In other words, it begins its separate life not as a matured creature, but as an infant which needs for a time to be watched and helped.

V.

The Dawning of Consciousness.