30. THE SUN-BATH.--Some also were accustomed daily to anoint themselves, and lie or walk in apartments arranged for the purpose, with naked bodies exposed to the direct rays of the sun. There is an interesting allusion to this practice, in a letter of the younger Pliny to the historian Tacitus, describing the destruction of Pompeii by an eruption of Vesuvius. "My uncle," (Pliny the elder,) "was at that time in command of the fleet at Misenum. On the 24th of August, about one in the afternoon, my mother desired him to notice a cloud which seemed of unusual shape and dimensions.

He had just returned from _taking the benefit of the sun_, and after a cold bath, and a slight repast, had retired to his study." Then follows a description of the destruction of Pompeii, and the death of the elder Pliny.

[Sidenote: 31. Benefit of the sun? Effect upon plants? Skin?]

31. We may judge somewhat of "the benefits of the sun," by observing the unnatural and undeveloped condition of plants and animals which are deprived of light. Plants become blanched and tender; the fish of {51} subterranean lakes, where no light enters, are undersized, and have no eyes; tadpoles kept in the dark do not develop into frogs; men growing up in mines are sallow, pale, and deformed. Besides the well-known effect of solar light in tanning the skin, it also makes it thicker and better able to resist exposure; though the complexion may be thereby injured, the health gains more than compensates for the loss of beauty. "To make good the loss of the lily, where the sun has cast his ray, he seldom fails to plant the rose."

[Sidenote: 32. Direction about clothing? Exposing limbs of children?

Clothing, night and day?]

32. CLOTHING.--In reference to clothing, we are far more apt, in our changeful climate, to use too little than too much. An aphorism of Boerhaave, worth remembering, if not of adopting, is, "We should put off our winter clothing on midsummer's day, and put it on again the day after."

He also says, "Only fools and beggars suffer from the cold; the latter not being able to get sufficient clothes, the others not having the sense to wear them." The practice of exposing the limbs and necks of young children, for the alleged purpose of "hardening" them, is quite hazardous. It is not to be denied that some seem to be made tough by the process; but it is so only with the rugged children, the delicate ones will invariably suffer under this fanciful treatment. As has been stated before, the skin is constantly acting, by night as well as by day. It is therefore conducive both to cleanliness and comfort to change entirely the clothing on retiring for the night. The day-clothing should be aired during the night, and the bedding should be aired in the morning, for the same reason.

[Sidenote: 33. Cosmetics? Painters' colic?]

33. POISONOUS COSMETICS.--The extensive use of _cosmetics_ for the complexion is a fertile source of disease. The majority of these preparations contain certain poisonous mineral substances, chiefly lead.

Now, the skin rapidly absorbs the fine particles of lead, and the system {52} experiences the same evil effects that are observed among the operatives in lead works and painters, namely, "painters' colic," and paralysis of the hands, called "wrist-drop."

34. Certain hair-dyes also contain lead, together with other noxious and filthy ingredients. These do not work as great harm as the cosmetics, since they are purposely kept away from the skin, but they rob the hair of its vitality. Eye-washes, too, are made from solutions of lead, and many an eye has been ruined by their use. They deposit a white metallic scale on the surface of the eye, which becomes a permanent obstruction to the vision.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What are the characteristics of the skin, and what office does it perform? 41 2. What can you state of the structure of the skin? 41 3. Describe the cuticle and tell its use. 41, 42 4. Describe the cutis or true skin and tell its use. 42 5. What can you state of the nature and growth of the nail? 42, 43 6. Of the nature and growth of the hair? 42, 43, 44 7. Of the offices performed by the nails and hair? 44 8. How is the difference in complexion in different persons accounted for? 44 9. How is the presence of freckles accounted for? 44 10. How does Nature provide a dressing for the hair? 44, 45 11. What other service do the sebaceous glands perform? 45 12. State what you can of the perspiratory glands. 45 13. What is the difference between sensible and insensible perspiration? 46 14. State the uses and importance of perspiration. 46, 47 15. What impurities gather naturally on the skin? 47 16. Repeat what is said of the importance of bathing. 47, 48 17. When should we indulge in cold, warm, and sea bathing? 48, 49 18. What is the effect in each case? 48 19. What directions are given as to the time and manner for bathing? 49 20. What is related of bathing among the ancients? 49, 50 21. What is related to show the antiquity of sun-bathing? 50 22. What are the effects of sun-bathing? 50, 51 23. What directions are given in relation to clothing the body? 51 24. What can you state of poisonous cosmetics? 51, 52 25. Of hair-dyes and eye-washes? 52

{53}

CHAPTER IV.

THE CHEMISTRY OF FOOD.

_The Source of Food--Inorganic Substances--Water--Salt--Lime--Iron--Organic Substances--Alb.u.men, Fibrin, and Casein--The Fats or Oils--The Sugars, Starch, and Gum--Stimulating Substances--Necessity of a Regulated Diet._

[Sidenote: 1. The term food? Source of food? Need of preparing food?]

1. THE SOURCE OF FOOD.--The term _food_ includes all those substances, whether liquid or solid, which are necessary for the nourishment of the body. The original source of all food is the earth, which the poet has fitly styled the "Mother of all living." In her bosom, and in the atmosphere about her, are contained all the elements on which life depends.

But man is unable to obtain nourishment directly from such crude chemical forms as he finds in the inorganic world. They must, with a few exceptions, be prepared for his use, by being transformed into new and higher combinations, more closely resembling the tissues of his own body.

[Sidenote: 2. Usefulness and hurtfulness of plants? What then must man do?

Parts of the same plant or tree?]

2. This transformation is effected, first, by the vegetable world. But all plants are not alike useful to man; while some are absolutely hurtful.

Accordingly, he must learn to discriminate between that which is poisonous and that which is life-supporting. Again, all parts of the same plant or tree are not alike beneficial: in some, the fruit, in others, the leaves, and in others, the seeds only are sufficiently refined for his use. These he must learn to select; he must also learn the proper modes of preparing each kind for his table, whether by cooking or other processes. {54}

[Sidenote: 3. Certain forms of vegetable creation? Example of the bee?

Cattle? The inference?]

3. Again, certain forms of the vegetable creation which are unfit, in their crude state, for man's food, and which he rejects, are chosen as food by some of the lower animals, and are, by them, made ready for his use. Thus the bee takes the clover, that man cannot eat, and from it collects honey.

The cattle eat the husks of corn and the dried gra.s.s, that are by far too coa.r.s.e for man, and in their own flesh convert them into tissues closely resembling his muscular tissue. In this way, by the aid of the transforming processes of the vegetable and animal creations, the simple chemical elements of the mineral kingdom are elaborated into our choice articles of food.

[Sidenote: 4. What cla.s.sification? Define organic substances. Inorganic.

Organic, how spoken of? The inorganic? Water and salt?]

4. INORGANIC SUBSTANCES.--The substances we use as food are cla.s.sified as _organic_ and _inorganic_. By organic substances are meant those derived from living forms, such as vegetables and animals. Inorganic substances are those simpler inanimate forms which belong to the mineral kingdom. The former alone are commonly spoken of as food, but the latter enter very largely into the const.i.tution of the body, and must therefore be present in our food. With the exception of two articles, water and common salt, these substances only enter the system when blended with organic substances.

[Sidenote: 5. Water in physiology? Where found? Computation? Water in the teeth? Muscle, tendons, and ligaments? How ascertained? Water in the fluids of the body? What is the advantage?]

5. WATER.--Water, from a physiological point of view, is the most important of all the articles of food. It is everywhere found in the body, even in the bones and the teeth. It has been computed that as large a proportion as two-thirds of the body is water. The teeth, the densest of the solids in the human system, contain ten per cent. of water. The muscles, tendons, and ligaments are more than half water; for it is found that they lose more than half their {55} weight when dried with moderate heat. But it is in the _fluids_ of the body that water is found most abundantly. It gives to them the power of holding a great variety of substances in solution, and is the great highway by which new supplies are conveyed to the point where they are required, and by which old particles of matter, that have served their uses, are brought to the outlets of the body to be thus removed from the system.

[Sidenote: 6. Length of time man can do without food or water? Give the comparison? Bulk of drinks? Const.i.tuent of meats, etc.? Fruits?]

6. Man can remain a longer time without solid food than without water. He may be deprived of the former for ten to twelve hours without great suffering, but deprivation of water for the same length of time will produce both severe pain and great weakness. The food should contain not less than two parts of water to one of solid nutriment. Water const.i.tutes the great bulk of all our drinks, and is also a large const.i.tuent of the meats, vegetables, and fruits which come upon the table. Fruits, especially, contain it in great abundance, and, in their proper season, furnish most agreeable and refreshing supplies of the needed fluid.

[Sidenote: 7. Salt, how obtained? Where found? In the human body?

Importance of salt? What else can you state of the value of salt?]

7. COMMON SALT.--Salt, or sodium chloride, as an article of food, is obtained chiefly from the mineral kingdom; although plants contain it in small quant.i.ties, and it is also found in the tissues of nearly all animals used as food. In the human body, it is an ingredient of all the solids and fluids. The importance of salt to animal life in general, is shown by the great appet.i.te for it manifested by domestic animals, and also by the habitual resort of herds of wild beasts to the "salt-licks" or springs. In those parts of the world where salt is obtained with difficulty, man places a very high price upon it.

[Sidenote: 8. Experiments upon animals?]

8. Experiments upon domestic animals show that the withdrawal of salt from their food, not only makes their {56} hides rough and causes the hair to fall out, but also interferes with the proper digestion of food. If it be withheld persistently, they become entirely unable to appropriate nourishment, and die of starvation.

[Sidenote: 9. Salt, how taken into the system? Its use in cooking?

Consumption?]

9. Salt is usually taken into the system in sufficient quant.i.ties in our food. Even the water we drink often has traces of it. The habitual use of much salt in cooking, or as a seasoning at the table, is not wise; and while it may not lead to consumption, as some writers declare, it is a bad habit in itself, and leads to the desire for other and more injurious condiments.

[Sidenote: 10. Lime in the bones? What does it impart? Chief ingredient of the bones and teeth? Where else found?]

10. LIME.--This is the mineral substance which we have spoken of before as entering very largely into the composition of the bones. It is the important element which gives solidity and permanence to the framework upon which the body is built. Calcium tri-phosphate, or "bone-earth," is the chief ingredient of the bones and teeth, but is found in the cartilages and other parts of the body in smaller quant.i.ties.

[Sidenote: 11. How does lime find its way into the body? Early life? Effect of its derivation?]

11. How does this substance find its way into the body? Meat, milk, and other articles obtained from the animal kingdom contain it, and it is abundantly stored away also in the grains from which our bread is made, in wheat, rye, and Indian corn. In early life, while the body is growing, the supplies of this substance should be carefully provided. The evil effects of the deprivation of it are too often and painfully evident in the softening of the bones, and in the predisposition to curvature of the spine--deformities which are most deplorable and which continue through life.

[Sidenote: 12. Iron, its abundance and diffusion? Where found? What part of the blood is it? How supplied to the system? In case of loss of blood or wasting disease?]

12. IRON.--This substance is probably the most abundant and widely diffused of the metals. It is found in {57} most of the vegetables, and is a very important component of animal tissues. It enters into the composition of human blood in about one part per thousand. Ordinarily, the food conveys to the system enough iron for its use, but it must sometimes be introduced separately as a remedy, especially after great loss of blood, or after some wasting disease. Under its influence the blood seems to be rapidly restored, and a natural color of the lips and skin replaces the pallor caused by disease.

[Sidenote: 13. Soda, potash, and magnesia? How do they occur?]

13. OTHER INORGANIC SUBSTANCES.--In addition to the substances mentioned, the mineral kingdom supplies compounds of soda, potash, and magnesia, which are essential for the use of the body. They occur in small quant.i.ties in the body, and enter it in combination with the various articles of diet.

[Sidenote: 14. Organic substances, whence derived? What do they comprise?

Groups?]