MOTHER: No; then when we enjoy the sweet flowers, we place them near the nostrils and draw a deep breath, and we say, “Ah, how sweet!” We do this so that more air will touch the nerves of Smell, which are in the upper part of the nose. These little nerves form the tiniest branches you can think of, and all unite in one large nerve, which goes to the brain. They quickly tell us about things we can neither taste nor see. They are thickly spread over this room of Smell, which is indeed a wonderful place. Here is a picture of the nerves of which I have been telling you. PERCY: I think in a dog Smell must have good nerves. [Illustration: _Nerves of Smell_] MOTHER: Yes; for some dogs will follow the footsteps of their master, though he has been out of sight for hours, and Smell is so keen that they use him in tracking game while hunting. Some Indians in South America can tell if a stranger comes near them, even in a dark night, by the use of Smell alone. They can also tell if a stranger is black or white. In some people Smell is much keener than in others. ELMER: When I had a cold last week, I couldn’t smell at all. MOTHER: Sometimes when one has a very bad cold, the opening into Smell’s room gets filled up so that odors can not get in. People having a disease called ca-tarrh´ often can not smell at all. HELEN: But of what use is Smell to us? MOTHER: First, he helps us to eat proper food. We are not apt to eat anything which has a bad odor; at least we should not do so. Smell might be said to be a twin brother to Taste, and part of his duty is to help Taste in selecting proper food for the body. Sometimes when dinner is cooking, I hear you say: “Oh, how good it smells! It makes me feel hungry.” [Illustration: “_Dogs will follow the footsteps of their master._”] PERCY: I have often felt that way, but I didn’t know it was Smell giving me an invitation to eat. MOTHER: Another way Smell cares for the body is by giving us warning against bad air. Sometimes a lot of tiny folk called “germs” get into the air and make it unfit to wash the blood. These germs are “seeds of sickness,” and should never be allowed to get inside the body. Sometimes they make the air smell bad, and then Smell sends word to the brain: “Look out! Don’t come here; for this bad air will make you ill.” AMY: And does that mean that the master should take the body away? MOTHER: Yes; or if we go into a room which is close and musty, and the air is full of germs, it means to open the doors and windows, and let the clean, pure air come in. Sometimes Smell gets so used to bad odors that he does not give warning as he should; so we should always heed his counsel at first. Any place or thing which has bad odors should never be near the house. HELEN: I think Smell must find some sleeping-rooms rather unpleasant places for him to stay in.