Mother: Its next trip may be taken to the brain, to help a little girl learn her lessons in school. The brain takes what it can use, and back the blood goes to the right heart, around through the bath room again, and the next time it may be sent to the liver, where it finds sugar and bile-making going on, as usual.
Elmer: But how can the blood be of any use there?
Mother: I think you would not ask such a question if you could go there to see. It “takes all the starch out of it,” as you sometimes say, and some other things besides, to make into sugar. It also uses part of it to make into bitter bile, so you may well believe that when it goes back to the heart there is not much left that is of value. But after a good wash in the bath room the blood goes back to the heart, and this time may be sent to the bones in your fingers, and they take what lime it has. This drop was just making its way back to the heart again when Amy cut her finger and let it out.
Percy: But I should have thought the blood would have been worn out making so many trips.
Mother: So it would if it was not made new by the food you eat. It keeps taking as well as giving as it goes round and round through the body. You would not expect a housekeeper to keep everything tidy and clean in a house, and not give her what she needed to make her strong and able to work; and so the master of the house gives the blood plenty to eat; and it makes no complaint as long as it can do its work well. It is a very busy person, we might say, and, as there is no end of things to do in the house in which you live, the blood works night and day.
Elmer: But I don’t see how the blood can take with it all that is needed to mend the different parts of the house.
Mother: It is supposed to carry with it a supply of everything that is needed to keep the house in order as it goes, so that when a bone says, “I want some lime,” or a muscle says, “Please give me some al-bu´men,” each part gets what it calls for if it is in the blood. Whether it has what every part needs depends on what the master of the house sends into the kitchen to make blood. Have I told you about the filters in the body?
Amy: I’m sure you have not. Please tell us now.
Mother: There are two of them in the lower part of the trunk close to the back, one on each side. They are the shape of a bean, and are called the kidneys. The blood passes through them, and some of the poisons it has picked up are strained out and sent to a storeroom, called the bladder, where they are kept till the brain gives an order to send them away.
