231.WHAT ARE THE SINUSES?
Every now and then you meet somebody whose nose seems all stuffed up, or he complains of pains in the eyes and cheeks, and headaches. When you ask him if he has a cold, he may answer: “No, I have sinus trouble.”
What is a sinus, and why do people get “sinus trouble?” Strictly speaking, a sinus is a space filled with blood or with air. But for most people, the expression “sinus trouble” means an infection of one of the cavities connected with the nose.
230.HOW DO WE SEE IN THREE DIMENSIONS?
When we look out across a field, how do we know one distant object is bigger than another, or that one is behind another? Why do we see everything in three dimensions, in proper relation to each other, instead of seeing everything “flat?”
The fact is that when we “see” things, we see them not only with our eyes, but with our minds as well. We see things in the light of experience. Our mind, based on certain experiences, helps us interpret what we see. And unless the mind can use the cues it has learned to interpret what we see, we can become very confused indeed.
229.HOW DO WE FALL ASLEEP?
We know pretty well what happens during sleep. Our body is inactive, we lose consciousness, and we fail to respond to things that are happening around us.
We also know a great deal of what takes place in our body during sleep. We know how the muscles relax, how certain vital functions continue, what happens to our circulation, our temperature, and so on.
