=Remember.= 1. It is a proved fact that diseases are transmitted to man by the bites of mosquitoes and wood-ticks. 2. It is possible to do away with both the mosquito and the wood-tick almost completely, although it requires a great deal of work and the expenditure of a large amount of money. 3. Health is the most valuable thing we have, and it is foolish to hesitate in giving the work and money necessary to exterminate disease-bearing insects, as well as the many other causes of sickness. CHAPTER XXII HOW TO KEEP GERMS OUT OF WOUNDS [Sidenote: How germs get through the skin] Germs get into our bodies through breaks in the skin. These breaks may be made by a cut or a scratch, by the bite of an insect, or even by the pulling out of a hair. There are some special germs, such as those which cause yellow fever, which are introduced by the bite of an insect; but at present we will consider only those germs that would naturally enter through any break in the skin. [Illustration: FIG. 50. Small, deep wounds are very liable to become infected.] [Sidenote: Effect of germs in wounds] The skin of the human body acts as an armor against certain germs that are constantly trying to get through it. There are several germs of this class. Some of them cause white pus, or matter, but this is the least dangerous kind of all. Another kind causes boils or even blood poisoning, and another kind causes erysipelas. We cannot get rid of these germs, for they are everywhere, to a greater or less degree; but they are more abundant in dirty than in clean places. They cause every degree of inflammation, from a slight redness of the skin to the blood poisoning that brings death. [Sidenote: Real cause of suppuration] Sometimes you will hear people say that a wound suppurated (that is, became inflamed and full of matter) because the blood was in bad condition. As a matter of fact, there would have been no suppuration if germs had not got into the wound. It was not the condition of the blood that caused the suppuration, but the germs. Sometimes, when only a few germs get into a wound, and when the cells of the body are all in good condition and doing their work properly, the suppuration will be very slight, because the healthy cells of the body will kill the germs. But if very many germs get in, even healthy body cells cannot kill them all. We have said that the germs which cause suppuration are everywhere, so it would seem almost impossible to keep them out of a wound. This is true in a sense; but even after they have got into a wound, you can wash them out if you use plenty of soap and water to cleanse the wound thoroughly. When I said that it is impossible to keep them out of a wound, I meant an accidental wound, for it is quite possible to keep them out of a wound that is made intentionally, as is done by the surgeon. [Sidenote: How the surgeon prevents suppuration]