Taste receptors monitor the quality of all the food ingested. They are intimately involved in both food acceptance and rejection. The sensation of taste is also important in the regulation of many specific chemicals necessary for maintenance of the body. For example, disturbance of the adrenal glands results in a change in the intake of salt which is necessary for regulation of the sodium balance. Curt Richter's early studies on specific hungers and preference thresholds initiated a large number of studies in this field. The relationship between taste and food intake is now well recognized by physiologists, psychologists and nutritionists. Our current concepts of the neural coding of taste quality and intensity are largely based upon the classical paper by PFAFFMANN in 1941. Many subsequent single nerve fiber studies have added to our understanding. In recent years Zotterman and Diamant have successfully recorded from the human taste nerves as they pass through the middle ear. This allowed them to study the relationships between the response of taste receptors and the resultant taste sensation. No similar feat has yet been accomplished with the visual and auditory systems.

Olfaction is involved intimately in two of the most basic functions of animals: food intake and reproduction. There are also many other involvements of olfaction in animal behavior, not the least being communication. The authors of this volume have collected and evaluated the comparative anatomy, electron microscopy, electrophysiology, genetics, psychology, chemistry, and biophysics of the olfactory system and then indicated their roles in animal behavior. The importance of olfaction in the everyday life of an animal is just being realized fully and recent years have brought forth a great surge of research in this area. The diverse dis ciplines that contribute to our understanding of olfaction make the development of this volume rewarding for those working in this field. The olfactory system's very high sensitivity and its great power of molecular discrimination interests many chemists and physicists. Data from the study of both vertebrates and insects show that only one molecule of certain odors is necessary to stimulate a single olfactory receptor The underlying physicochemical events are not yet understood. Also, many mammals can discriminate quickly the difference between two odors of similar structure. Thus the olfactory epithelium and the more centrally located neural components present the ultimate in chemical detection and analysis by a biological system. The principles involved are probably common to those of many other organs."