TASTE 



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consists of cells located conveniently on the surface of the 

 body where the dissolved materials will come in contact 

 with them. The cells which make up the organ are al- 

 ways exposed directly to the outside, with no protective 

 skin between (Fig. 36). To lessen the likelihood of in- 

 jury they are often located in little pockets or hollows 

 of some sort. In land animals the chemical sense can 

 be aroused both by substances in solution in water and 



Fig. 36. — Diagram of an organ of chemical sense, (a) the place 

 where the sensitive cells are directly exposed to the exterior. 



by materials which are present in the air in the form of 

 gas. It is quite true that these latter substances dis- 

 solve in the moisture which overlies the cells of the sense 

 organ before acting upon it, so that, strictly speaking, 

 the chemical sense in land animals operates as in aquatic 

 animals through substances in solution. 



Taste. — In the higher animals the organs for chemi- 

 cal sense are of two kinds to fit them for reacting to 

 chemical substances which reach the body by the two 

 different channels suggested above, i.e., in the food or 

 drink which is taken into the mouth, or in the air which 



