A Treatise on Hygiene (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. Excerpt from book: Section 3SECTION II. OF THE AGENTS INHERENT IN THE ORGANISM WHICH AFFECT THE HYGIENIC CONDITION OF MAN. CHAPTER I. RACE. The several races of men are distinguished by great differences, so great that they can scarcely be regarded as due to any other cause than a diversity of origin. Climate, hunger, destitution, depravity, disease, exposure, degradation will, in the course of time, work many alterations in the form and aspect of organic beings; but they cannot so alter original types as to cause a race, whether of plants or animals, to lose its identity. Thus, the several varieties of the cabbage are all derived from a wild plant, scarcely edible, growing on the sea-coast rocks of Great Britain. The many kinds of apples all come from a common stock?the crab-apple. The peach, the most luscious of our fruits, has its origin in the bitter almond of Persia. Yet, however much these fruits may have varied from the parent growth, they all evince a tendency to return to the original form when separated from the influences which have given rise to the deviation. So with the various alterations which animals have undergone, through the action of a changed mode of life, or a different climate, continuing through several generations. Restore them to their former conditions of existence, and in a short time the original type is reached. Take, for example, the sheep. The fleece of this animal consists of two kinds of wool intermingled: one is formed of coarse, stiff hairs; the other of short, fine, curly wool. In the merino sheep this latter is greatly in excess, and hence the value set upon fabrics made of it; but if the animal is removed to a colder region than is natural to it, the coarse, straight hair takes the place of the softer variety, and the value of the whole growth is lost. Replace the merino sheep in ...