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.
The object of rest is not merely to add to man’s happiness and enjoyment, to give him time for pleasure. It is to recuperate his body and mind. If he were to go on using his muscles without any relaxation they would gradually waste, and after a time would waste rapidly and to a serious extent. If he were to exercise his mind without any respite, the delicate brain-cells would become exhausted, for like the muscles they would have no chance of renewing themselves.
Strong, hardy sailors who have had to undergo a prolonged physical strain, as in the case of shipwreck, have been known to suffer ever afterwards from debility; their hearts and muscles had been over-exerted to such an extent that they were never able to recover themselves. And people who have had to go through a long stretch of brain work have lain in a stupor for weeks afterwards, unable to use their minds or even know what was going on around them.