Debbie DelBove, age 15, of Staten Island, New York, for her question

How do our noses detect the smell of food?

Notice how the smell of vanilla reminds you of the taste of vanilla flavored goodies such as ice cream and cakes. A sizzling barbecue wafts odors that remind us of the mouth watering flavors of beef and blended spices. Obviously the sense of smell is related to the sense of taste in some way. The system also works in the opposite direction. The odor of rotten fish tends to provoke a gagging sensation. The odor of a bad egg is revolting because one's smell taste system reports that the item would be most objectionable to the palate.

The olfactory organ, alias the sniffer, is a specially adapted cavity situated in back of the nose, above the roof of the mouth. Air passes by it on its way to and from the lungs. This means that we smell as we breathe and every unusual whiff in the air is brought to our attention. The sniffing chamber is lined with loosely pleated folds of pink skin. This membrane is beset with sensory cells that sprout tiny hairs. It also has cells that secrete mucous material that keeps the skin moist. The sensory cells are nerve endings. The fine nerves lead back inside the skull to the smelling center in the brain.

All odors, pleasant or otherwide, are gaseous molecules mixed with the air. They are widely assorted chemicals that blend with the moist mucus of the olfactory organ and spark chemical reaction in its sensory cells. This data is relayed to the brain. There it is analyzed and promptly integrated with other sensory systems.

Meantime, the brain constantly evaluates and stores data from the taste buds in the mouth. In its own mysterious way it compares these two streams of smell and taste data and sometimes the smell and taste systems seem to swap or share their information. This is why a whiff of sizzling hamburger can spark the taste buds to drool and provoke the appetite to expect a banquet.

This exchange of data is odd because the two systems do not react to the same things. The nose can detect burnt and acid odors, fragrant and rancid odors. The various taste buds can detect sweet and sour flavors, bitter and salty flavors. The multitude of smells we can detect are subtle blends of just four basic odors. The multitude of tastes are complex blends of just four basic flavors. Somehow the various smells and tastes of foods often merge in a related system.. We smell as we breathe and interesting food data may be shared with the taste buds and they in turn may share the flavorsome data from certain foods with the olfactory system.

Just a few gaseous molecules in a breath of air can spark the olfactory chemical reaction and almost at once the brain detects a highly complex odor. For example, suppose the various olfactory sensors relay a whiff of six parts fragrant and four parts acid, three parts rancid and two parts burnt. The brain interprets this subtle blend as the fragrance of a rose. However, one's talented sniffer tends to tire. After detecting roses, hamburgers or some other odor for some time it seems to lose interest. Enough is enough and we soon fail to notice the roses or to drool over the food.