XIII.] THE FROG. 241 



d. Open the nasal cavity of a frog wliicli has been pre- 

 served in Miiller's fluid ; gently scrape away a little of 

 the epithelium lining the chamber, mount in water : 

 examine with your highest power. 



a. Among numerous mutilated cells, a certain number 

 of more or less perfect ones will be found : these 

 are of two kinds, viz. large columnar epithelial cells 

 (J. 1. 6), each with an oval nucleus, an unbranched 

 peripheral process and a branched deeper one; 

 and smaller cells, with less protoplasm around the 

 nucleus and finer peripheral and central processes. 



d. The gustatory organ. 



1. The shape and arrangement of the frog's tongue have 

 already been described (B. 11. a). 



a. Snip off a bit of mucous membrane from tbe 

 upper surface of the tongue of a recently killed 

 frog, mount in normal saline solution and cover 

 in plenty of the fluid with a large coverslip : ex- 

 amine with one inch obj. 



a. On the surface of the fragment and especially 

 around its edges numerous minute elevations 

 of the surface will be seen : these are the pa- 

 pillce : some (filiform papillce) are pointed at 

 the free end and others (fungiform papillce) 

 flattened. Note the loops which the blood ca- 

 pillaries make in some of the papillae. 



^. Examine one of the thinner bits of the speci- 

 men with a higher power : the papillae will be 

 seen to be covered by epithelium, which is for 

 the most part ciliated (J. 1. c) ; some of the 

 papillse however will be seen to have no cilia 

 except a narrow belt around the somewhat 

 M. 16 



