"Architecture" means "the art or science of building or construction," and "Mental Architecture" means "the art or science of Mind Building." By "Mind Building" I, of course, mean "Brain Building," for as I have told you in a previous chapter, the brain is the "machinery" of the personal manifestation of mind, or the "converter" or "transformer" of the Mind-Power. But as the word "mind" is generally used as synonymous with "brain," in the case of individuals, I shall speak of "Mind Building" in this lesson, although I always mean "Brain Building" when I so speak.

The differing manifestations of mind in the various persons with whom we come in contact is at once recognized as depending upon the character, quality, degree and grade of their brain-material The brain is composed of a peculiar substance called "plasm," or elementary living-matter. The word "plasm" is derived from the Greek word meaning "a mould or matrix," and its use in connection with the brain-substance is peculiarly appropriate, for it is in the cells of the brain that "mental states" are "cast or moulded," as it were. The brain is composed of an enormous number of tiny cells which are the actual elements in the production and manifestation of thought, or mentation. These brain-cells are estimated at from 500,000,000 to 2,000,000,-000, according to the mental activity of the person. There is always a great number of reserve brain-cells remaining unused in every brain, the estimate being made that even in the case of the wisest man, or most active thinker, there are always several millions of unused brain cells held as a reserve. And the most advanced science also informs us that the brain "grows" additional cells to meet any demand upon it. And brain-building is the development and growth of brain-cells in any special region of the brain; for, as you probably know, the brain contains many regions, each region being the seat of some particular function, quality, faculty or mental activity. By developing the brain-cells in any special region, the quality, activity or faculty which has that region for its seat is necessarily greatly increased and rendered more effective and powerful.

The investigators along the lines of Phrenology have long since recognized the fact that brain-centers or regions could be developed by proper exercises, etc., and the text-books on that science give us many interesting facts regarding the same. These cases show us that not only is an individual able to develop and cultivate certain qualities of mind on the one hand, or restrain them on the other, but that also the very outward shape and size of the skull manifests a corresponding change, for the bony structure accommodates itself very gradually to the pressure of the increasing number of cells in some particular center or region of the brain. It is a fully demonstrated scientific fact that a man may "make himself over" mentally, if he will but devote the same degree of attention, patience and work to the subject that he would in the case of a desired development of some part of the physical body - some muscle, for instance. And the processes are almost identical in the case of muscle and brain-center - use, exercise and practice along the lines pointed out by those who have investigated and experimented along the particular line.

Prof. Elmer Gates, of Washington, D. C, one of the most remarkable men of this age, has given to the world an account of some remarkable experiments along the line of brain-growing, the experiments having been tried upon various animals. He tells us that his early experiments along this line were in the direction of training dogs to develop some one particular sense, that of seeing or hearing particularly. He would specially train a certain number of the animals according to his methods, and at the same time would keep a like number of the same animals of the same age, etc., without any extraordinary use of the particular faculty in question, and still a similar number without the opportunity of using that faculty at all. At the end of a certain time he would kill some of the animals belonging to each class, and upon examining the brains of each he made the discovery that the number of brain-cells (in the regions of their brains in which the sense or faculty was manifested) showed a startling difference, depending upon the degree of use and exercise of the particular faculty. His specially trained animals showed a much greater number of brain-cells than had ever been found in animals of the same breed and age. Prof. Gates continued these experiments over a number of years and obtained some remarkable results. He specially trained the faculties of some of bis dogs so that they were able to distinguish between seven shades of red and a like number of green shades. I have not the time here to speak at length of the wonderful results of Prof. Gates' experiments, hut he has firmly established the scientific fact that brains may be "grown" at will, if the person will apply himself to the subject with sufficient zeal and ardor. I have conducted a number of interesting experiments (not with dogs, or through vivisection, however) which have proven conclusively to my mind that the entire natures, dispositions, characters and faculties of people may he entirely changed by intelligent psychological methods along the lines of Suggestion or Auto-Sugges-tion, accompanied with certain other methods to be mentioned in this lesson.

The great school of "New Thought" people of the various sects, cults and associations have been doing some excellent work along these lines during the past ten years or more. Their systems of "affirmations" and "denials" really developed or restrained their brain-centers and desirable qualities were increased and developed and undesirable ones were restrained. But the mere use of "affirmations." "auto-suggestions" or evert strong, positive suggestions given by another, forms only one-third of the work necessary in order to produce the best results. It is all very well to assert "I am Brave," "I am Industrious," "I am Active," etc., etc., but if the work stops there it remains only one-third done. It is true that these affirmations and auto-suggestions undoubtedly do stimulate and develop mental faculties and brain-centers and play an important part in character building. But in order that they be used to the best advantage there must be visualization, and there should be a certain physical acting out of the mental suggestions or affirmation. There must be seeing and doing as well as saying.