SMELL AND TASTE 205 



the tongue and does not come into contact with the taste- 

 bulbs there you will hardly notice it ; but if you are clumsy 

 and let it touch the bulbs at the back you will appreciate its 

 character to the full. Why does strong bitterness make so 

 many people start sneezing? This is a point that has not, 

 I believe, been investigated. As far as we know all the other 

 mammals, and indeed all the other vertebrates, taste as we 

 do, though many of the flavours that they obviously enjoy 

 would be disgusting to us. On the other hand, many of our 

 likes and dislikes may be due to education and custom rather 

 than any innate preference. If cheese was eaten only by some 

 remote tribe of savages we should probably think it was 

 revolting to enjoy the flavour of the coagulated secretion of 

 the modified skin-glands of a cow after it had undergone 

 bacterial decomposition. And how many people really enjoy 

 the taste — or flavour — of their first glass of beer? Not for 

 nothing have we the expression — "an acquired taste". 



It is when we come to aquatic animals that we find it 

 difficult to draw the line between taste and smell. Both are 

 chemical senses that respond to substances dissolved in the 

 water, coming from objects at a distance or in contact. How 

 close must the contact be before smell gives place to taste? 

 It is very doubtful whether the sensation felt by an aquatic 

 animal is different whether water containing dissolved sub- 

 stances comes from far or near. It is, perhaps, best to lump 

 the two together under the blanket label "chemo-receptor". 

 The skin of fishes contains numerous sense receptors scattered 

 all over it, some of which resemble in structure the taste- 

 bulbs of higher vertebrates, and in a few fishes they also 

 occur inside the mouth. The nose in fishes does not, with 

 very few exceptions, lead into the mouth, but consists of a 

 pit on the snout lined with chemo-receptor cells. In the bony 

 fishes it is generally divided into two, so that there are two 

 separate nostrils on each side of the head. The surface area 

 of the inside of the pit is increased by the lining being thrown 

 into numerous folds or ridges. It is sensitive to many sub- 

 stances in very great dilution, as is shown by the way in 

 which some kinds of fish are immediately attracted to food 

 put into the water at a distance. Experiments have shown 

 that they are indeed attracted by chemo-reception and not 



