XXV.J TASTE AND SMELL. 261 



/8. The rod-cells, (taste-cells) with spheri- 

 cal or ovoid nucleus, rod-shaped hyaline 

 peripheral and central processes. 



i. Nerve fibres running along the dermis of the 

 papillae, and branching off to the buds. Note 

 also the layers of striated muscle and the 

 glands of the tongue, comparing the general 

 structure with that of the cesophagus (Lesson 

 XVI. B.) and of the skin (Lesson xxiv. A.). 



4. Tease out a small piece of a papilla foliata which 

 has been placed in osmic acid "2 p.c. for one or 

 two days, and observe the characters of the cells 

 of the taste-buds, noting the branched central 

 process of the rod-cells. 



B. Sense of Taste and Shell. 



1. Pinching the nose tightly, so as to suspend the 

 sense of smeU, attempt with the eyes shut to 

 distinguish by taste between pieces of an apple, 

 an onion, and a potato; they will taste alike. 

 The pieces must not be rubbed against the 

 mouth with the tongue, or they will be recog- 

 nized by their different consistency. 



2. Wipe the tongue quite dry, and place on the tip 



a crystal of sugar or on the back a crystal of 

 sulphate of quinine ; neither will be tasted until 

 it is dissolved. 



3. -A-pply with pointed, non-polarizable electrodes 

 (cp. Appendix) a constant current to the tongue ; 



