This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
The brain, like the muscles, is improved and strengthened by exercise and injured by overwork or idleness; and just as a man may specially develop one set of muscles and neglect the rest until they degenerate, so he may do with his brain; developing one set of intellectual faculties and leaving the rest to lie fallow until, at last, he almost loses the power of using them at all. The fierceness of the battle of life nowadays especially tends to produce such lopsided mental development. How often does one meet the business man, so absorbed in money-getting that he has lost all power of appreciating any but the lower sensuous pleasures; the intellectual joys of art, science, and literature have no charm for him; he is a mere money-making machine. One, also, not unfrequently meets the scientific man with no appreciation of art or literature; and literary men utterly incapable of sympathy with science. A good collegiate education in early life, on a broad basis of mathematics, literature, and natural science, is the best security against such deformed mental growth.
What happens when we have very frequently repeated an action? Point out why it is desirable, even on physiological grounds, to form good habits. How does every thought or act influence the nervous system? What is the consequence of yielding to temptation? What of resisting it?
The Primary Effects Of A Moderate Dose Of Diluted Alcohol, as a glass of whiskey and water, on one unaccustomed to it, are to cause temporary congestion of the stomach; dilatation of blood-vessels of the skin, indicated by the flushed face ; a more rapid beat of the heart ;* nervous excitement, exhibited by restlessness and talkativeness. Then some incoherence of ideas, and often giddiness. Finally there is a tendency to sleep. On awaking the person has some feeling of depression, not much appetite, and is in general a little out of sorts for a day.