[Sidenote: Introspective Knowledge] We have been considering the relationship between mind and body from the standpoint of the mind. Our investigation has been largely introspective; that is to say, we simply looked within ourselves and considered the effects of our mental operations upon our own bodies. The facts we had before us were facts of which we had direct knowledge. We did not have to go out and seek them in the mental and bodily activities of other persons. We found them here within ourselves, inherent in our consciousness. To observe them we had merely to turn the spotlight into the hidden channels of our own minds. [Sidenote: Dissection and the Governing Consciousness] We come now to examine the mind's influence upon the body from the standpoint of the body. To do this we must go forth and investigate. We must use eye, ear and hand. We must use the forceps and scalpel and microscope of the anatomist and physiologist. [Sidenote: Subordinate Mental Units] _But it is well worth while that we should do this. For our investigation will show a bodily structure peculiarly adapted to control by a governing consciousness. It will reveal to the eye a physical mechanism peculiarly fitted for the dissemination of intelligence throughout the body. And, most of all, it will disclose the existence within the body of subordinate mental units, each capable of receiving, understanding and acting upon the intelligence thus submitted. And we shall have strongly corroborative evidence of the mind's complete control over every function of the body._ Examine a green plant and you will observe that it is composed of numerous parts, each of which has some special function to perform. The roots absorb food and drink from the soil. The leaves breathe in carbonic acid from the air and transform it into the living substance of the plant. Every plant has, therefore, an anatomical structure, its parts and tissues visible to the naked eye. [Sidenote: What the Microscope Shows] Put one of these tissues under a microscope and you will find that it consists of a _honeycomb of small compartments or units_. These compartments are called "cells," and the structure of all plant tissues is described as "cellular." Wherever you may look in any plant, you will find these cells making up its tissues. The activity of any part or tissue of the plant, and consequently all of the activities of the plant as a whole, are but the combined and co-operating activities of the various individual cells of which the tissues are composed. _The living cell, therefore, is at the basis of all plant life._ [Sidenote: The Little Universe Beyond] In the same way, if you turn to the structure of any animal, you will find that it is composed of parts or organs made up of different kinds of tissues, and these tissues examined under a microscope will disclose a cellular structure similar to that exhibited by the plant.