8. Detection of arsenic in beer. Fix up the apparatus shown in fig. 29 A. The tube (a) is filled with fragments of calcium chloride to dry the gas. Put into the bottle some pure zinc and pure dilute hydrochloric

Fig. 29A.

acid. When all the air has been expelled and the hydrogen is freely coming off light it at the jet and heat the constricted part of the tube (c). There should be no deposit on the tube at the heated part. Then pour into the flask some of the beer to be tested and some more pure hydrochloric acid. Continue heating the constricted part of the tube. If arsenic is present in the beer a stain will be produced on the hot tube. This is arsenic, and it may be distinguished from other similar stains by its solubility in a solution of sodium hypochlorite.

AD. HYG.

8

CHAPTER V.

PERSONAL HYGIENE-EXERCISE-HABITS.

THE judicious combination of exercise, rest, and sleep plays a very important part in the health of the individual. Lack of exercise is soon followed by atrophy, or wasting away of the parts that are not used. A muscle that is not exercised, but lies idle, soon wastes away and becomes useless. This is particularly noticeable in the case of a broken or paralysed limb. The lack of use soon produces wasting and loss of power of the limb. The brain also, when not exercised by study and reading, does not develop to its fullest possible extent. On the other hand, unless the exercise is combined with the proper amount of rest, the results are even more disastrous, as the body becomes overworked and exhausted.

Exercise is necessary at all periods of life, but especially so during childhood and early manhood or womanhood. It is the duty of all parents to see that their children enter into the school games, and spend a great deal of time in the open air. Practically all schools have now adopted physical exercises as part of their curriculum in recognition of the importance of these to the children. In the case of adults the exercise that should be indulged in must depend upon the nature of the daily work. Thus, if a man is doing bodily work all day, his muscles have had quite sufficient exercise, and mental exercise is what he needs for his spare time. On the other hand, those whose occupation is sedentary, such as clerks, students, etc., need physical exercise in their spare time, in order to bring their muscular, circulatory, and respiratory systems to the proper pitch of development.

For any beneficial result, the exercise taken must be systematic and regular, and not indulged in by fits and starts. By gradually and steadily increasing the work done by them, a set of muscles may be greatly increased in size, but there is a limit to this increase, and if the work be carried to excess the muscles will begin to waste away. Care should be taken to give every muscle of the body its necessary exercise. Many of our sports are faulty in leaving most of the muscles idle. The best real exercise for all the muscles is probably obtained by boxing, lawn tennis, and Rugby football.

Violent exercise should never be taken without proper training. By training, we do not mean the old-fashioned idea of feeding a man on limited rations of half-raw meat, but simply an outdoor life, with plenty of good, nourishing food, and no lack of exercise for all the muscles. Violent exercise, without proper training of this kind, is likely to lead to most disastrous results, the commonest of which is heart disease resulting from overstrain.

Some of the physiological effects of exercise deserve. special mention. We have already mentioned that the muscles are increased in size and are rendered capable of doing more work. By exercise they are also brought more under the control of the will. The first effect of exercise is, perhaps, the quickening of the heart beat and the rate of respiration. The heart beats more rapidly and more forcibly, causing an increased flow of blood through the blood vessels all over the body. If the exercise be sudden and violent, the heart may be incapable of meeting this sudden demand upon it, and the valves may be rendered incompetent, giving rise to heart disease. But by gradually increasing the exercise, the heart is strengthened and the coats of the arteries are made stronger and healthier.

Respiration is also quickened by exercise. The amount of air taken in at each inspiration is increased, and larger quantities of water and carbon dioxide are given out in the expired air. Thus, a man at rest draws into his lungs each minute about 480 cubic inches of air, but if walking at the rate of three miles per hour he takes in 1550 cubic

inches of air, and if he increases his rate to six miles per hour, the amount of air that he inspires is raised to 3250 cubic inches.

The

The skin acts freely while exercise is being taken. blood vessels surrounding the sweat glands are distended with blood, and the secretion of sweat is increased. In this way an extra quantity of waste matter is removed from the body by the skin.

Other effects of exercise include the exhilaration and strengthening of the nervous system, the improvement of the appetite and digestion, and the stimulation of the kidneys and bowels, thereby aiding the elimination of waste matters from the body.

Rest. Without proper rest the organs of the body would soon become worn out. The most absolute rest is that obtained by sleep. The amount of sleep required varies with the age and occupation, but, speaking generally, the average adult requires 7 or 8 hours sleep a day. Children require more sleep than adults because their bodies are working at a greater rate, and they are more easily exhausted: those under 4 years should have 16 hours sleep a day; from 4 to 12 years of age they require 12 hours sleep; from 12 to 16, 10 hours sleep is

necessary.

The sleeping-room should be quiet and well ventilated. Bedsteads should always be used, if possible, as sleeping upon the floor is less healthy on account of the interference with the free circulation of air around and under the sleeper, and also the increased liability to inhale dust or gases from the floor. A hair mattress is very much to be preferred to a feather bed. Infants should not sleep with adults, as the risk of "overlaying" is very great under these circumstances. They should always sleep in a separate bed or cot, which may be easily constructed out of an ordinary clothes'-basket or box.

Habits. Either good or bad habits are bound to be formed by children as they grow up, and so it behoves all good parents to see that the habits that the children form are those which are conducive to their health and happiThe habit of eating slowly and chewing the food

ness.

well, and of having regular meals has already been referred to. The danger of forming the habit of taking alcoholic drinks has also been mentioned. Among the necessary and important habits are cleanliness, proper attention to the teeth, and the regular action of the bowels.

The teeth should be cleaned regularly once or twice a day. If cleaned only once a day the best time is night, just before retiring to rest. A good tooth powder is a mixture of equal parts of salt and carbonate of soda, When any signs of decay of the teeth appear they should be stopped by a dentist. The teeth of children should be systematically examined for traces of decay or signs of irregularity. Irregularity can often be corrected to some extent by a skilful dentist.

The bowels should be freely opened at least once a day. The best way to secure this is to cultivate the habit of evacuating the bowels at the same time each day. If a regular habit is not formed, constipation is bound to occur, and this will produce indigestion, hæmorrhoids or piles, and sometimes inflammation of the bowels. Aperients should rarely be needed. A far better way to procure proper action of the bowels is to take regular exercise, and eat brown bread, oatmeal, vegetables, and fruit.

Causes of Disease.

The causes of disease are usually divided into two groups, viz. (a) predisposing, and (b) determining. (a) Predisposing causes are certain conditions of the body, e.g. temperament, idiosyncrasy and constitution, which increase its liability to disease. (b) Determining causes are those which actually produce the disease. "Thus, if a big man stands up to be shot at in a duel, he is more likely to be hit, other things being equal, than a small one; and so his size is a predisposing cause in favour of his being killed. If he is killed, it is the bullet which is the determining cause" (Corfield). Similarly with such a disease as consumption, occupation, lack of sufficient air space, and heredity may be said to be predisposing causes, but the determining cause is the invasion of the lungs by the