Monthly Archives: April 2014
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.
207.WHAT IS A TAPEWORM?
This certainly isn’t a pleasant subject, but many people suffer from tapeworm and so there is great curiosity about it. A kind of flatworm, the tapeworm is an intestinal parasite.
This means that it lives in the digestive tract of another animal, called the host, and is fed by food which the host has partly digested.
