Suppose the needle you use is dirty, just see what a state of things may occur. Your needle is dirty—it is swarming with germs. You prick the blister with it—that is, you introduce into a cavity filled with warm solution of albumen the organisms of putrefaction. This is just what the microbes like, and they will rapidly render the contents of the blister putrid. And now neither the microbes nor the matter can escape, for the prick has long ago become obliterated. Nor can you apply anything to kill these germs or promote healing. The third way to treat a blister is to cut away the whole of the cuticle confining it. This is dead skin, and so removing it causes no harm. You can now apply an antiseptic ointment to the raw surface. The best is an ointment of boracic acid, oil of eucalyptus and vaseline. Oh, but when you cut open the blister, do you not let the germs in? Yes, you do, unless you have been scrupulously careful that everything you used was perfectly clean. But even if you have introduced germs, it is not so very serious here, for you apply the ointment directly to the raw surface. So now the microbes get the worst of it. There is nothing for them to eat; there is nothing preventing them from getting away; and there is a (to them) poisonous ointment applied directly to them. We said everything you use must be clean. We must therefore tell you how to sterilise needles, scissors, etc. You are usually told to sterilise instruments by passing them through a flame. Now this has many disadvantages. In the first place, merely passing a knife through a flame does not even warm it. Then, if you leave it in the flame long enough, you spoil its temper and make it dirty with soot. By far the best way to sterilise instruments is to boil them. Sterilise your needles, etc., by boiling them in solution of carbolic acid in a test-tube. To treat burns, what must we add to our chest? Boracic acid ointment, that is all. Now for fractures. If you are taking a drive with a friend, and the horse bolts, and you are both thrown out, but you escape uninjured, while your friend breaks her arm or leg, what are you going to do? You are going to “set” the fracture, are you? Oh, no, you are not! Not if your friend has her wits about her. Have you ever set a fracture before? Have you ever seen a fracture set? Do you know anything about setting a fracture? Of course you do not. You would find that setting a fracture was not the simple thing you think it is.