Part 20

How often we hear someone remark upon the wonders of heredity. People are astonished because John should look like John's father. As a matter of fact, the astonishment should come the other way. The child is but a continuation of the life of the parents. The cells from which the child develops have within them the power to grow and to produce individuals like the parents. This is wonderful, but it is only another form of the wonder of a willow twig growing into a willow tree when placed in moist earth.

To the scientist, then, the wonder comes, not in the fact that the child resembles the parent, but in the fact that the child is not identical with the parent. Part of the explanation of this lack of identity, or, as it is known to science, variation, is due to the fact of sexual reproduction; that is, to the fact that the child has two parents instead of one.

The physiological process which takes place in the union of two reproductive cells is truly most wonderful. Of late years this has been studied under powerful microscopes and has resulted in some very wonderful revelations of the mysteries of Nature.

The nucleus (center of growth) of the parent cells contains little thread-like structures known as chromosoms. These chromosoms are considered to be the physical basis of heredity. In each species of animal there is a definite and a different number.

When the sperm-cell unites with the female or germ-cell, these thread-like chromosoms pair off and unite each chromosom with the corresponding structure from the other cell. The combined structures then divide, and half of each chromosom is cast out of the cell-nucleus, and plays no part in the life of the future being; the other half is retained and divides as each new cell is formed.

Thus we see that every part of the new individual is the result of the fusion or combination of the two parents. This explains the variation of inheritance, and through this source must be traced all traits of heredity. After the original fusion of these microscopic physical elements of heredity, the future development of the individual is wholly a matter of environment and nutrition.

WHAT HEREDITY IS

What heredity is and what it is not will now be considered in a practical way. It is clearly a matter of heredity that a man is born a man and not a monkey. Likewise, it is clearly a matter of heredity that distinguishes the various races of men. We could go farther and trace out and describe many of the physical distinctions which mark families, and even individuals, such as general size of frame, form of countenance, color of hair and eyes, etc.

Among mental traits we can safely ascribe to heredity only general distinctions. Intellectual parents are more likely to give birth to intellectual children than are parents whose natural mental faculties are less developed. There is also no doubt that certain natural characteristics of mind, such as quick temper, musical ability, etc., may be inherited. The belief, however, in the inheritance of many less distinct features, both physical and mental, is not well established by scientific investigation. Strength of muscle, control of the nervous system, susceptibility to, or freedom from dis-ease, etc., are more matters of nutrition and environment than of inheritance. The idea that consumption, alcoholism, etc., are inherited, or that the education or training of parents along certain lines will result in children with faculties adapted to similar education, is not in accordance with scientific knowledge.

SUMMARY OF FACTS REGARDING SEX AND HEREDITY

1 The function of sex has been developed in the process of evolution for the purpose of perpetuating life.

2 The sexual functions are very closely related to the life of the individual, and can be normal only when the laws of nutrition and of general hygiene are observed.

3 The idea of prenatal culture as commonly taught is a delusion; the only method that the mother can employ to control the growth of her unborn child is to live a wholesome, normal life, physically and mentally, and thus supply her own body and that of the child with perfect material for the building of living cells.

4 The powers of heredity are often overestimated, and many of the weaknesses and disorders of life supposed to be inherent can be overcome by proper nutrition and environment. All life, whatever be the inherited tendencies, will be developed to the highest possible capacity by obeying the laws of individual growth, for in the individual, as in the race, Nature is always striving to bring the products of her work to the highest degrees of perfection.

LESSON XXI

REST AND SLEEP

REST

Throughout all nature we observe the phenomena of universal rhythm, manifested in opposing forces, such as heat and cold, light and darkness, construction and destruction, etc. The human body is as much affected by this rhythm as is any other form of life.

There are two forces continually at work within us, one toward destruction and disintegration, and the other toward construction and upbuilding. The common physiological terms for these activities are "waste" and "repair," and we observe them as one of the distinct manifestations of the universal laws of growth, progress, and evolution.

History moves in cycles. Even the life of nations depends somewhat upon this same principle of the interplay of the positive and negative forces of life.

We see the same thing in the changes of the seasons upon the face of the earth. Throughout autumn and winter there is a process of decay, death, and disintegration; leaves fall; plants and vegetables die; fruits ripen, fall and decay. This process continues until former beautiful and symmetrical bodies of matter are thoroughly disintegrated, and the particles once composing them are separated into their original elements, to be appropriated in new manifestations of life in springtime and summer.

We are inclined to think of the human body as a machine--a marvelous, intricate, and complex mechanism which serves our will and our desires; as a tool with which we work out our earthly destiny. But unlike man-made machines, it is self-repairing, self-adjusting, and contains within itself the forces of construction, which are constantly tending toward perfection, while our industrial machines are constantly tending toward their own disintegration and destruction.

Every movement of the body, conscious or unconscious, even thought and emotion, use up some part of the body-tissue which must be replaced by new material. This constant change in the texture and the make-up of the body we call "metabolism," involving the functions of digestion, absorption, assimilation, and elimination.

While we may regard the body as a machine, there are many points in which the favorite comparison to a steam-engine is not exact.

The inert metal composing the steam-engine has no power in itself, nor does power act through the different particles of metal, but it is controlled by the external application of force, which is the result of chemical changes caused by combustion in the fire-box. The metal of the engine has no part in the production of this energy. It does not need to take periods for rest, and if it were possible to supply it continually with water and fuel, it could run steadily from the time it was started until one or more of its essential parts were destroyed through friction.

But the engineer and the fireman who drive the engine find it necessary to rest from their labors at certain intervals, not merely for fuel and water, but to prevent serious destruction of body-tissue. This is true because man is compelled by hitherto unrecognized laws to give his body an opportunity, not only for readjustment in its composition, but also for the actual renewal of that power which animates him and makes him an intelligent, self-adjusting, and self-controlled being.

THE OLD PHYSIOLOGY

According to the teachings of the old physiology, our stomachs were fire-boxes of the human engine; food was fuel, and the stomach was supposed to transform this fuel into work or energy by a process not entirely clear. Just as it is impossible for the lifeless iron and steel, within itself to transform coal and water into dynamic power, and to apply that power to its own locomotion, so it is impossible and entirely incompatible with reason for mere muscular tissue of the body to extract enough energy from the food we eat to perform the work necessary for that transformation itself, besides enough more to carry on all the functional activities of the system, and at the same time to do hundreds of foot-tons of physical labor. In this fact lies the key to some understanding of the phenomenon of rest and sleep.