198 physiology and morphology of animals. 



of its taste. The urgency of appetite in mammals for- 

 bids the leisurely enjoyment of taste as such. 



Birds have no teeth. They do not masticate, but 

 bolt their food. In many cases, too, their food, as, for 

 example, seeds and the like, is hard and tasteless. It is 

 probable, therefore, that their sense of taste is more 

 imperfect than that of mammals. 



Reptiles, amphibians, and fishes all swallow their food 

 without mastication. They have teeth ; but they are 

 prehensile, not masticatory. We know little of their 

 sense of taste, but it is probably feeble. 



Of taste among invertebrates we know nothing, except 

 in the case of insects. These are doubtless attracted to 

 food mainly by smell; but sweets — sugar, honey, nectar 

 of flowers — are sought and enjoyed by bees, ants, 

 butterflies, and flies. 



THE SENSE OF TOUCH AND ITS ORGANS. 



Here, again, and even more than in the case of taste, 

 scientific discussion is impossible without analysis. The 

 word feeling includes very many distinct sensations. 

 For example: lay the hand on the table, palm upward, 

 (i) Lay a card across the finger tips; we have a sense or 

 feeling of contact. (2) Instead of a card let it be a ten- 

 pound weight ; we now have in addition a feeling of 

 pressure. (3) Let the weight be fifty pounds; we have 

 now in addition a feeling of pain. (4) Let the weight 

 be hot or cold ; we have now a corresponding feeling of 

 heat or cold. (5) Now lift the hand from the table; 

 in addition to all the preceding, we have a feeling of 

 weight or resistance to our muscular effort — we feel the 

 heft. Thus, then, there are many kinds of sensations in- 

 cluded in the word feeling. These are so different that 

 they are probably perceived by different specialized 

 nerves. It is almost certain, according to recent obser- 



