Mysteries of Taste and Smell.

Kaipara and Waitemata Echo, 22 May 1914, Page 2

Mysteries of Taste and Smell.

IN THE DARK ONIONS TASTE LIKE APPLES. The two senses of taste and smell ! are effected by means of end-organs embedded in the mucous membranes : (those parts of the skin which are ! coated by mucus, as, for instance, ' the inside of the mouth) of the ' tongue and the upper third of the j nasal cavities ; nerves leading from i them to the nervous centres in the j brain ; and the brain centres of j taste and smell respectively. The ; end-organs are simply cells of the mucous membranes somewhat modi- : fied and specialised to receive the I minute filaments of the nerves of taste and. smell. The nerves are bundles of extremely fine filaments united to form a trunk, while the -nerve centres in the brain are clusters of cells concerned in the perception of taste and smell. Any tasty or odoriferous substance must first come in contact with the end organs of taste or smell, as the case may be, and from there the sensation is carried to centres in the brain by means of the nerves, just as a telegraph1 message is carried by wires. That is, says Dr. J. A. Husik, whom we quote, for example, if. placed upon the tongue it must first be dissolved by the salivary secretion of the mouth before the sensation of sweetness can be experienced. There are in the main four taste ■sensations. These are : Sweet., bittet*, salty and sour or acid. Metallic and alkaline tastes are regarded by some as real tastes, by •others as a . mixture of the sensation of taste and that of touch.

i Not all the parts of the tongue are equally sensitive to all the tastes. Thus the tip of the tongue is especially responsive to sweetness. The base of the tongue is sensitive to bitter tastes. The tip and sides are capable of perceiving salty tastes. Sour or acid taste is felt upon all sides. It must be remembered that the sense of taste is closely interlinked •with the senses of vision and of odour. Thus, for example, with eyes ' shut v and nostrils tightly closed, it is difficult to distinguish between an apple, a potato, or an onion. Cinnamon, under similar circumstances, will taste like slightly sweetened Hour. In order that a substance may have odour it must be volatile. That is, it must be capable of giving off minute particles in a gaseous form. Again, when these particles reach the nasal mucous membrane they must be soluble in the mucous fluid which constantly bathes it. In the absence of these two properties no substance will have colour. Unlike,, tastes, odours have no names. We classify them as pleasant and unpleasant. It is often said, for example, that chloroform has a sweetish odour. This merely serves to show the close relationship that exists between the senses of taste and smell. Odour cannot, ! strickly speaking,, be sweet. The word "sweet," uaed in connection with odour, is ordinarily understood to mean highly pleasant. Persons often speak of a pungent odour or a pungent taste. This is an erroneous form of speech. Pun- j gency is neither a taste nor a smell. It is due to strong stimulation by certain substances upon the nerves of common sensation, or touch, residing in the mucous mem- j branes of the tongue and nose. The essential nature of the twin senses of taste and smell is not understood. For example, it is still not known whether these sensations are brought about by physical or chemical changes in the structures perceiving them. Still more difficult is it to comprehend what is the mysterious nature of the process whereby we not only taste and smell but are also made cognizant of the fact that such sensations are present. Between the centres of taste and smell and the higher thinking faculties of the brain some process must take place whereby a sensation as of taste or smell, is translated into an idea or a thought that taste or j smell is being experienced.—" Popular Science Siftings." .