CHAPTER III.
PHYSIOLOGY OF SIGHT, SMELL, AND TASTE.
From Comparative Anatomy we pass to Physiology. Instinct is in harmony with itself. The beast which eats flesh delights in the sight and smell, as well as in the taste of a mangled victim. While his prey is alive, the very sight or smell of it attracts him; but the sight of herbage, roots, and fruits, gives him no pleasure, and excites no action. On the contrary, the herbivorous animal is attracted by the verdant mead, and there selects unerringly the plants best suited to it. Here again sight, smell, and taste are gratified in harmony. The same remarks apply to those animals whose instincts lead them to feed on decaying animal or vegetable matter. Objects to us most revolting gratify all their senses at once. When by sight, smell, and taste an object allures man to eat, we may believe such object to be his natural and reasonable food.
Sight.—Of all the things in the form of food, fine fruit most attracts the eye of man, and by the very sight makes his mouth water. Nothing is so strong a temptation to the young. Other objects, when artificially prepared and associated with previous enjoyment, will (I am aware) excite similar feelings; but no article of food so much as fruit entices a taste which has not been vitiated by acquired habits.
Smell.—The smell also of fruit peculiarly allures man, and our power of discriminating fruits by smell is considerable. Man (says Dr. Roget) "distinguishes vegetable odours more accurately than those proceeding from animal substances. The reverse is observed with regard to quadrupeds whose habits are decidedly carnivorous."
Certain hunting beasts, as eminently the dog and jackal, perceive an odour even when prodigiously diluted by distance or by evaporation: this is called power of scent. Yet animals which need to smell, like the sheep, solely at substances near at hand, are believed to have more discrimination in their smell. This again associates man with the vegetable feeders. "Man" (says Müller, "Elements of Physiology," ii., p. 1317), "is far inferior to carnivorous animals in acuteuess of smell; but his sphere of susceptibility to odours is more uniform and extended." Smell not only warns the lungs of noxious emanations, but guides animals to their natural diet. Undoubtedly our artificial state has impaired in us this instinct. We cannot, like the sheep or ox, distinguish this herbage from that by smell; and, in fact, such food is not adapted to us. But if from birth to manhood we had fed naturally, there is every reason to believe that our faculty of smell would discriminate right and wrong in food.
