1.We may begin our study of taste and smell by making a very simple experiment.Get a raw potato，peel it，cut it into slices，and wrap these up in pieces of clean paper.Do the same with an onion，taking care to hold it in a cloth while cutting it up，and to remove the cloth and the knife，so that no smell of the onion remains in the room.Then blindfold a friend，place him on a chair，and explain what he is to do.He is to hold his nose with his hand，and then he is to get a piece of fruit put into his mouth.He must chew the fruit，and guess what it is.You are to mention several fruits，and he is to nod his head when you come to the right one.
2.When he is ready，you slip a piece of the potato into his mouth.He will perhaps guess that it is an apple or a pear；but as soon as he takes his hand away from his nose，so that he can smell，he will know that it is a potato.You can then try the same experiment with the onion；and even the onion will not be recognized until the nose is brought into use.
3.This shows that it is to our noses and not to our tongues that we owe the power of distinguishing from each other the flavours of fruits，and of a hundredother things which in common language we are said to taste.It is only the saline or salt，the sweet，the acid or sour，and the bitter substances that we really taste.Many substances，like table salt，have no smell at all，and it is by our tongue alone that we recognize them.
4.The nerves of smell，or olfactory nerves，arisefrom the delicatelining of the nose，high up beyondthe nostrils，and pass directly to the brain.Many animals have more sensitive noses than we have.The foxhound can detect the odour of the fox on the turf an hour or more after it has passed swiftly over the spot，and the bloodhound can recognize the scent of a particular man as easily as you can recognize his face.
5.Turning now to the sense of taste，we find that the tongue and the back of the throat are both capable of tasting.Sweet，sour，and salt substances are best tasted by the tip，the side，and the middle of the tongue，while bitter substances are tasted at the back alone.If youtaste some quinine，or chew some hop leaves，you willfind that the bitter taste is not felt until some of the substance gets to the back of the mouth.
6.The nerves of taste，or gustatory nerves，arise inthe red skin of the tongue and the back of the mouth，probably in little tiny projections or papillae ，which areof various kinds.Round the edge and also on the top of the tongue are scattered a few big papillae，which often look like little red spots.Between these are others，more numerous and much smaller.At the back of the tongue，so far back that it is very difficult to see them，are some fifteen or twenty large papillae-as large，infact，as small warts.They are probably the spots wherethe taste nerves for bitter substances arise.
7.We cannot taste everything.Chalk and sand，for example，are tasteless.A substance must be dissolved in the saliva or juice of the mouth before it can be tasted，and chalk and sand cannot be dissolved.Among thesubstances which can be dissolvedin the saliva，thereare some which have no taste at all，such as the white of an unboiled egg，pure starch，paste，and gum；but the list of such substances is not a long one.If you think over the matter，you will find that，as a rule，substances which have a pleasant taste and smell are good for food；while，on the contrary，things that have an unpleasant taste and smell are hurtful when we eat or drink them.
8.We have therefore two senses guarding us from danger.They are placed in the mouth and the nose，ready to direct us in the choice of food.If we followed the leading of these senses more obediently，it would