42 The Animal Mind 



animal's possible consciousness? The first thought which 

 strikes us in this connection is that the number of different 

 sensations occurring in an Amoeba's mind, if it has one, is 

 very much smaller than the number forming the constituent ele- 

 ments of our own experience. We human beings have the 

 power to discriminate several thousand different qualities 

 of color, brightness, tone, noise, temperature, pressure, pain, 

 smell, taste, and other sensation classes. Thus the content 

 of our consciousness is capable of a great deal of variety. It 

 is hard to see how more than three or four qualitatively dif- 

 ferent processes can enter into the conscious experience of an 

 Amoeba. The negative reaction is given to all forms of strong 

 stimulation alike, with the single exception of food. We shall 

 in the following chapter discuss more fully the nature of the 

 evidence that helps us to conjecture the existence of different 

 sensation qualities in an animal's mind ; but it is clear that 

 where an animal so simple in its structure as the Amoeba 

 makes no difference in its reactions to various stimuli, there 

 can be no reason for supposing that if it is conscious, it is 

 aware of them as different. The reaction to edible sub- 

 stances is, however, unlike that to other stimulations. The 

 peculiarity of edible substances which occasions this differ- 

 ence must be a chemical one. In our own case, the classes 

 of sensation which result from the chemical peculiarities of 

 food substances are smell and taste ; evidently to a water- 

 dwelling animal smell and taste would be practically indis- 

 tinguishable. We may say, then, that supposing conscious- 

 ness to exist in so primitive an animal as the Amceba, we 

 have evidence for the appearance in it of a specific sensation 

 quality representing the chemical or food sense, and standing 

 for the whole class of sensations resulting from our own 

 organs of smell and taste. The significance of the positive 

 reaction is harder to determine. It seems to be given in re- 



