Chap. V.] 



GENERAL HISTOLOGY. 



77 



sides of two folds are seen four taste-buds imbedded in the 

 epithelium and connected with nerve fibres at their inner ends. 

 At ii. one of these taste-buds is shown on a larger scale. 



(c.) Smell. In the olfactory membrane of the nose certain 

 elongated spindle-shaped cells are wedged in between the more 



FIG. 27. XERVE-ESDTXOS. 



i. Taste-buds of papilla foliata of rabbit, ii. A bud enlarged, iii. Olfactory 

 cells (dog), iv. Retina of frog. 1. Pigmented epithelium. 2. Rods and 

 cones; between this and 3 is a structureless limiting membrane. 3. Outer 

 nuclear layer. 4. Outer molecular layer. 5. Inner nuclear layer. 6. Inner 

 molecular layer. 7. Layer of nerve cells. 8. Layer of nerve fibres. The 

 layer marked 8 is turned towards the source of light, and is bounded by 

 a structureless limiting membrane. 



ordinary epithelium cells as indicated in 27, iii. These are in 

 connection with the ultimate endings of the olfactory nerve. 



(d.) Hearing. Somewhat similar spindle-shaped cells produced 

 into long auditory hairs are found in special regions of the organ 

 of hearing, and are in connection with the auditory nerve. 



(e.) Sight. The most complex of nerve-endings are those of the 

 optic nerve in the retina of the eye. Fig. 27, iv. gives a section 

 of the frog's retina under a high power (). There are eight 

 distinct layers : 1. pigmented epithelium : 2. the layer of rods 

 and cones ; 3. the outer nuclear layer ; 4. the outer molecular 

 layer ; 5. the inner nuclear layer ; 6. the inner molecular layer ; 

 7. the layer of nerve cells ; 8. the layer of nerve fibres. The 

 last layer, that of nerve fibres, is the most internal, nearest the 

 centre of the eyeball, and presented towards the rays of light. 

 But the light vibrations are received by the ends of the rods and 

 cones in the pigmented epithelium, and then transmitted to the 



