210.WHAT IS FAT?
BROWN FAT
Everybody today is so weight-conscious, and so many people are on diets, that you could probably say fat is something nobody wants.
Yet fat, of course, is very necessary to the body. It accumulates in this way: At certain points, the connective-tissue cells become filled with fat. First, tiny droplets appear inside the cells. They increase in size, run together into a large drop, and finally fill the cell and swell it out like a balloon. Eventually, the cell is changed into a large drop of fat surrounded by a thin envelope of tissue.
209.WHAT IS AN ODOR?
Everybody likes pleasant odors—the perfume of flowers, or the aroma of a cake baking. But a disagreeable odor can be quite unpleasant. The strange thing is that the amount of odor in both pleasant and unpleasant cases can be very, very tiny! Did you know that we can detect the odor of certain substances if only one part of 30,000,000,000 parts by weight is present in a given weight of air? And this is true of man—whose sense of smell is a fraction as good as that of a dog!
208.WHAT IS AN ENZYME?
The body of every living animal and plant is a chemical factory. In fact, if all kinds of chemical changes weren’t constantly taking place, life would be impossible. You are able to use food, breathe, grow, and move because of the chemical changes which take place m the cells, tissues, and organs of your body.
Here is an example of this chemical life process. You eat a piece of bread, or a cereal, or a potato. The starch in this food is changed into sugars which go into the blood. There they are burned by the oxygen which is in the air you breathe, and your body obtains energy.
