THE HIGHER ORGANISMS 



167 



at the base of the wings in some flies and upon the caudal 

 appendages of other flies may be olfactory in nature. 



Among vertebrates the sense of smell is always situated 

 in the nose, upon the mucous membranes of which the 

 olfactory nerves distribute in varying number according 

 to the activity of the sense. These nerves communicate 

 with the olfactory lobes of the brain and constitute an 

 added source of complexity to that organ. 



Taste. This is another amplification and specializa- 



Process of 

 neuro-epi- 



Epithe- Nerve- thelial Taste- 

 lium. fibrils. cell. pore. 



Tegmental 



cell. 



Neuro-epithe- 

 lial cell. 



Sustentacular 

 cell. 



Terminal 

 branches of 

 nerves. 



Fio. 66. Schematic representation of a taste-goblet. Bohm, Dairidoff, and 



Huber.) 



tion of the chemotropic irritability of protoplasm. As 

 in the highest animals, this sense resides in certain dis- 

 tributed nerve endings in the tongue and palate, does 

 not take the form of a visible sensory organ, and so is 

 not easy to localize. Little can be learned about it in 

 animals whose structure is essentially dissimilar. 



It would seem as though it must be almost universal 

 among animals as the chief means of discriminating 

 between what is useful and what is useless as food, yet 



