The phrase “day and night, Sunday and week-day” is a significant one. It expresses the need for periodic rest as imposed by Nature. Loss of sleep is equally harmful, whether it be due to work or pleasure. And whatever views people may hold in regard to the old-fashioned Sunday, when considered from a religious point of view, there is only one when we look at it from the medical side. Change is rest, as we shall have occasion shortly to emphasise, but the increasing tendency to rush off motoring and golfing on Sundays is not change, for the simple reason that most of the people who indulge in these pursuits are the very ones who motor and golf most days of the week. The old-fashioned Sabbath was no doubt carried to the opposite extreme, but it did at any rate infuse an atmosphere of restfulness, which is lacking in these days. [Sidenote: What rest is.] It is not that we wish to encourage idleness. That is a very different thing from rest, which implies cessation from work. There is a form of languor due to want of exercise, and we meet with people who are always tired because they lounge about too much. But there are others who are constantly feeling languid because they have not learned how and when to take suitable rest. Some people are always on the go. They habitually walk beyond their proper pace and rush at their work and their amusements with feverish anxiety. Even when they are playing golf, they hurry after the ball as though they were afraid it would run away from them if they did not catch it up. To people of this type illness, which is usually regarded as a misfortune, often proves a blessing in disguise. For it has one great advantage, in that it imposes upon the system the much-needed rest which has been denied it. We compared the human body to an engine. Yet in one respect this simile falls short. For man is a living being, and it is on this account that he needs something that the engine can do without. The marvellously delicate machinery of his body must have rest. An engine is liable to wear and tear, no matter how well it may be put together; even if it is made of the best metal to be obtained, and constructed as nearly perfectly as possible, there is always bound to be a certain amount of friction and concussion, which will in time lower its quality and impair its efficiency. But the machinery of the human system is subject to more than simple wear and tear; for there is, as we have seen already, a chemical process constantly taking place, which produces waste matter that must be drained away every day of our lives. Yet in spite of this, it is in a vastly better position than the engine, for it possesses at the same time a faculty of self-repair. We cannot take out parts and replace them by spare ones, but we do not need to do so. The most marvellous thing about the human system is the fact that waste and repair go on simultaneously. But in order that this may take place the system must have periodic rest.