By keeping the mouth shut you prevent yourself from getting thirsty when you are doing hard work. And also at night if you are in the habit of breathing through the nose it prevents snoring, and snoring is a dangerous thing if you are sleeping anywhere in an enemy's country. Therefore practise keeping your mouth shut and breathing through your nose at all times.
EARS.
A scout must be able to hear well. Generally the ears are very delicate and once damaged are apt to become incurably deaf. People are too apt to fiddle about with their ears in cleaning them by putting the corners of handkerchiefs, hairpins and so on into them, and also stuffing them up with hard cotton wool, all of which are dangerous with such a delicate organ as the ear, the drum of the ear being a very delicate, tightly-stretched skin which is easily damaged. Very many children have had the drums of their ears permanently injured by getting a box on the ear.
EYES.
A scout, of course, must have particularly good eyesight; he must be able to see anything very quickly and to see at a long way off. By practising your eyes in looking at things at a great distance they will grow stronger. While you are young you should save your eyes as much as possible, or they are not strong when you get older: therefore avoid reading by lamplight as much as possible and also sit with your back or side to the light when doing any work during the day; if you sit facing the light it strains your eyes.
The strain of the eyes is a very common failure with growing boys, although very often they do not know it, and headaches come most frequently from the eyes being strained; frowning on the part of a boy is very generally a sign that his eyes are being strained.
A scout, besides having good eyesight, must be able to tell the colour of things which he sees. Colour blindness is a great infliction which some boys suffer from. It takes away a pleasure from them, and it also makes them useless for certain trades and professions.
For instance, a railway signalman or engine-driver or a sailor would not be much good if he couldn't tell the difference between red and green.
It can very often be cured, and a simple way of doing this, if you find you are rather colour blind, is to get a collection of little bits of wool, or paper, of every different kind of colour, and pick out which you think is red, blue, yellow, green, and so on, and then get someone to tell you where you were right and where wrong. Then you go at it again, and in time you will find yourself improving, until you have no difficulty in recognising the right colours. It is better still to practise by looking at coloured lights at night in chemists' shops, railway signals, etc.