GENERAL ZOOLOGY 



Tectorial membrane 



Hair cell 



Supporting cell 



Basilar membrane 

 ^Auditory nerve fibers 

 Fig. 4.18. Organ of Gorli; semidiagrammatic (cf. Fig. 4.4). 



many lower animals (Fig. 4.19.-1 and p. 523). When the olfactory receptors 

 are stimulated by odors, the impulses that arise are conducted to the brain 

 over processes of the receptor cells. There is a rapid loss of sensitivity on 

 continued exposure to any particular odor, but this does not interfere with 

 responses to other odors. 



Taste buds, more widely distributed in aquatic vertebrates, are confined to 

 the tongue in mammals (Figs. 4.20 and 4A9B). There are four different 

 kinds of gustatory cells or taste receptors, which makes it possible for man to 

 discriminate four sensations of taste — sweet, sour, bitter, and salty. Taste 

 and smell are inseparable in our reactions to various foods and beverages. 



The cutaneous sensations are touch, temperature, and pain. Receptors for 

 touch are particularly concentrated in the finger tips and are sensitive to slight 

 deformation of the skin in which they are located. There are two types of 



Surface 



Supporting 

 cell 



Olfactory cell 



Pore 



Surface of tongue 



Gustatory cell 

 Supporting cell 



— Nerve fibers 



Fig. 4.19. A, cells of olfactory epithelium from the human nose, fi, cells of a taste bud in 

 epithelium of the tongue. In both cases, the sensory cells terminate externally in hair-like 

 processes that are able to receive the chemical stimuli of olfaction, or smell, and gustation, or 

 taste, respectively. 



no 



