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<h2>CHAPTER LI.</h2> 1009. Why do we perspire? Because the skin is filled with very minute pores, which act as outlets for a portion of the water of the blood, that serves to moisten and cool the surface of the body, and to carry away some of the matter no longer needed in the system. 1010. How is the perspiration formed? By very small glands, which lie embedded in the skin. It is estimated that there are about 2,700,000 perspiratory glands distributed over the surface of the body, and that these glands find outlets for their secretion through no less than seven millions of pores. 1011. What is insensible perspiration? Insensible perspiration is that transmission of watery particles through the skin which is constantly going on, but which takes place so gently that it cannot be perceived. It is, however, very important in its results, as no less than from twenty to thirty-three ounces of water may pass imperceptibly through the skin in twenty-four hours. 1012. What is sensible perspiration? [Pg 245] Sensible perspiration is that moisture which exudes upon the skin in drops large enough to be perceptible, when the body is heated by exercise or other means. <hr class="bible-verse" /> "And Elisha sent a message unto him, saying, Go and wash in Jordan seven times, and thy flesh shall come again to thee, and thou shalt be clean."—II kings v. <hr class="bible-verse" /> 1013. Why does a sudden change from heat to cold bring on illness? Because the effect of cold arrests the action of the vessels of the skin, and suddenly throws upon the internal organs the excretory labour which the skin should have sustained. 1014. Why does a chill upon the skin frequently produce inflammation of the lungs? Because the lungs and the skin together discharge the chief proportion of the watery fluid of the body. When the skin's action is checked, the lungs have to throw off a much greater amount of fluid. The lungs, therefore, become over worked, and inflammatory action sets in. 1015. Why does cleanliness promote health? Because every atom of dirt which lodges upon the surface of the body serves to clog and check the working of those minute pores, by which much of the fluid of the body is changed and purified. In the internal parts of the system, the Creator has made ample provision for cleanliness. Every organ is so constituted that it cleanses and lubricates itself. Every surface of the inner body is perfectly clean, and as soft as silk. Nature leaves to man the care of those surfaces which are under his immediate observation and controul; and he who, from idleness, or indifference to nature's laws, is guilty of personal neglect, opposes the evident intentions of the Creator, and must sooner or later pay the penalty of disobedience. 1016. Why does exercise promote health? Because it assists all the functions upon which life depend. It quickens the circulation, and thereby nourishes every part of the body, causing the bones to become firm, and the muscles to become full and healthy. It promotes breathing, by which oxygen is taken into the system, and carbon thrown off, and thereby it produces a higher degree of organic life and strength than would otherwise exist. It [Pg 246] promotes perspiration, by which, through the millions of pores of the skin, much of the fluid of the body is changed and purified. And it induces that genial and diffused warmth, which is one of the chief conditions of a high degree of vitality. <hr class="bible-verse" /> "Love not sleep lest thou come to poverty: open thine eyes, and thou shalt be satisfied with bread."—Prov. xx. <hr class="bible-verse" /> 1017. Why do we feel fatigue? Because those organs which stimulate the mechanism of the body to act, themselves require rest and repair. When the brain and nerves arrive at that state, they make their condition known to the system generally, by indications which we denominate fatigue. 1018. Why, after rest, do we return invigorated to our labours? Because the nervous system has accumulated, during the hours of rest, a fresh amount of that vital force which we call the nervous fluid, and by which the various organs of the body are excited to perform the duties assigned to them. 1019. What is sleep? Sleep is understood to be that state of the body in which the relation of the brain to some parts of the body is temporarily suspended. There are some parts of the body that never sleep: such are the heart, the lungs, the organs of circulation, and those parts of the nervous system that direct their operations. But when sleep overtakes the system, it seems as if the relations of those parts under the controul of the will were temporarily suspended; as if, for instance, those nerves which move the arms, the legs, the eyes, the tongue, &c., were all at once unfastened, just as the strings of an instrument are relaxed by the turning of a key, or the throwing down of a bridge over which they were stretched. What is meant by the temporary suspension of the relation of the brain to some parts of the body, may be thus explained. Notice a man when he sits dosing in a chair: at first his head is held up, the brain controlling the muscles of the neck, and keeping the head erect. But drowsiness comes on, the brain begins to withdraw its influence, and the muscles of the neck becoming as it were "unstrung," the head drops down upon the breast. But the sleep is unsound, and disturbed by surrounding noises. The brain is therefore frequently excited to return its influence to the muscles, and draw up the head of [Pg 247] the sleeper. He gives a sudden start, every muscle is tightened in an instant, up goes the head, the eyes open, the ears listen, until a feeling of security and composure returns; the sleep again deepens, the nervous connection is again withdrawn, and then down drops the head as before. <hr class="bible-verse" /> "Yet a little sleep, a little slumber, a little folding of the hands to sleep: So shall thy poverty come as one that travelleth; and thy want as an armed man."—Proverbs xxv. <hr class="bible-verse" /> 1020. Why do we dream? Dreams appear to arise from the excitement of the brain during those hours when its connection with the other parts of the living organism is suspended. For instance: a man dreams that he is pursued by a furious animal, and the mind passes through all the excitement of flying from danger; but the connection between the moving power, and the machinery of motion being suspended, no motion takes place. The same impressions upon the brain, when the nerves were "strung" to the muscles, would have caused a rapid flight, and a vigorous effort to escape from the apprehended danger. 1021. Why do suppers, when indigestible substances are eaten, produce dreaming? Probably because, as the digestive organs are oppressed, and those parts of the nervous system which stimulate the organs of digestion are excited by excessive action, those portions of the brain which are not immediately employed by the digestive process are disturbed by that sympathy which is observed to prevail between the relative parts and functions of the body. 1022. Why do we yawn? Because, as we become weary, the nervous impulses which direct the respiratory movements are enfeebled. It has been said that those movements are involuntary, and that the parts engaged in producing them are not subject to fatigue. But the operation of breathing is, to some extent, voluntary, though when we cease to direct it voluntarily, it is involuntarily continued by organs which know no fatigue. When, therefore, we feel weary—still controuling our breathing in our efforts to move or to speak—there frequently arrives a period when, for a few seconds, the respiratory process is suspended. It seems to be the point at which the voluntary nerves of respiration are about to deliver their office over to the involuntary nerves; but [Pg 248] the pause in the respiration has caused a momentary deficiency of breath, and the involuntary nerves of respiration, coming suddenly to the aid of the lungs, cause a spasmodic action of the parts involved, and a yawn, attended by a deep inspiration to compensate for the cessation of breathing, are the result. <hr class="bible-verse" /> "And it shall be, when they say unto thee, Wherefore sighed thou that thou shalt answer, For the tidings, because it cometh; and every heart shall melt, and all hands shall be feeble."—Ezekiel xxi. <hr class="bible-verse" /> 1023. Why do we cough? Because the respiratory organs are excited by the presence of some body foreign or unnatural to them. A cough is an effort on the part of the air tubes to free themselves from some source of irritation. And so important are the organs of breathing to the welfare of the body, that the muscles of the chest, back, and abdomen, unite in the endeavour to get rid of the exciting substance. 1024. Why do we sneeze? Because particles of matter enter the nostrils and excite the nerves of feeling and of smell. In sneezing, as in coughing, the effort is to free the parts affected from the intrusion of some matters of an objectionable nature. And in this case, as in the former one, there is a very general sympathy of other organs with the part affected, and an energetic effort to get rid of the evil. 1025. Why do we sigh? The action of sighing arises from very similar causes to those of yawning. But in sighing, the nervous depression is caused by grief; while in yawning, it is the result of fatigue. In sighing, the effect is generally erased by an expiration—in yawning by an inspiration. The mind, wearied and weakened by sorrow, omits for a few seconds to continue the respiratory process; and then suddenly there comes an involuntary expiration of the breath, causing a faint sound as it passes the organs of the voice. 1026. Why do we laugh? Laughing is caused by the very opposite influences that produce sighing. The nervous system is highly excited by some external cause. The impression is so intense, and the mind so fixed upon it, that the respiratory process is irregular, and uncontrolled. Persons [Pg 249] excited to a fit of laughter generally hold their breath until they can hold it no longer, and then suddenly there is a quick expiration causing eccentric sounds, the mind being too intently fixed upon the cause of excitement, either to moderate the sounds, or to controul the breathing. <hr class="bible-verse" /> "Except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air."—Corinth. xiv. <hr class="bible-verse" /> 1027. Why do we hiccough? Hiccough is caused by a spasmodic twitching of the diaphragm, a thin muscular membrane which divides the chest from the abdomen. It generally arises from sympathy with the stomach; and it is highly probable that the muscular twitches and jerks are so many efforts on the part of the diaphragm to assist the stomach to get rid of some undigested matter. 1028. Why do we snore? Snoring is caused by air sweeping through the passages that lead from the mouth through the nostrils, and which, in our waking moments, are capable of certain muscular modifications to adapt them to our breathing. But as in sleeping the nervous controul over them is withdrawn, they are left to the action of the air which, in sweeping by them, sets them in vibration. <div style="break-after:column;"></div>

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