Page:Popular Science Monthly Volume 52.djvu/451



HE mind, in the sense in which I shall here use the word, is the collective function of the sensorium or brain of man and animals. It is the sum total of all psychic changes, actions, and reactions. Under the head of psychic functions are included all operations of the nervous system, as well as operations of like nature which take place in creatures without specialized nerve fibers or nerve cells.

As thus defined, mental operations are not necessarily or exclusively conscious. With the lower animals nearly all of them are automatic and unconscious. Even with man, most of them must be so. But between the automatic and the conscious actions no sharp line of division exists. All functions of the nervous system are alike in nature, and from the present point of view may be considered together. Consciousness is not an entity, but a condition. It stands related to mind much as flame is related to fire.

It is a recognized law in biology that "function precedes structure." To define this law more exactly, we should say that function precedes the differentiation of the organ on which it depends. There is a certain work to be done, and a certain body of cells are set apart sooner or later to do it. Just as plowing was done in some fashion before the invention of the plow, so in some manner respiration was accomplished before the development of gills and lungs. Something of mental action came before there was ever an organized brain.

In the animals of one cell, or protozoa, breathing and digestion are each performed by the whole body. In the division of labor or