196 KISSES 



Even as recognised by the less acute olfactory sense of 

 man, the number and variety of agreeable and of dis- 

 agreeable scents, produced by various species of animals 

 and plants, is very considerable. But there is no doubt 

 that the number and variety discriminated by such animals 

 as dogs and many of the other hairy, warm-blooded beasts 

 is far greater. The nature of the particles given off by 

 odorous bodies which act on the nerve-endings of the 

 organs of smell of animals, is remarkable. They are vola- 

 tile ; that is to say, they are thrown off from their source 

 and float in the air in a state of extreme subdivision. 

 Unlike the particles which act upon the nerves of taste, 

 they are not necessarily soluble in water, and though often 

 spread through and carried by liquids, are in fact rarely 

 dissolved in water. The dissolved particles which act 

 upon the nerves of taste can be distinguished by man into 

 four groups — sweet, sour, bitter, and saline. But no such 

 classification of " smells " is possible. As a rule mankind 

 confuses the " taste " of things with their accompanying 

 " smell." The finer flavours of food and drink not included 

 in the four classes of tastes are really due to odoriferous 

 particles present in the food or drink, which act on the 

 terminations of the olfactory nerves in the recesses of 

 the nose, and excite no sensation through the nerves of 

 taste. 



The part of the brain from which the nerves of smell 

 arise is of relatively enormous size in the lower vertebrates 

 — as much as one fifth of the volume of the entire brain 

 in fishes — a fact which seems to indicate great importance 

 for the sense of smell in those forms. Even in the mammals 

 (the hairy, warm-blooded, young-suckling beasts) the size 

 of the olfactory lobes of the brain and of the olfactory 

 nerves, and the labyrinthine chambers of the nose on which 

 the nerves are spread, is very large, as one may see by 

 looking at a mammal's skull divided into right and left 



