250 ELEMENTARY BIOLOGY. [CHAP. 



lies between the two and completely separates 

 them. 



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

 served in Mailer'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 num- 

 ber of more or less perfect ones will be found : 

 these are of two kinds, viz. large columnar epi- 

 thelial cells (J. i. b\ each with an oval nucleus, 

 an unbranched peripheral process and a branched 

 deeper one ; and smaller cells, with less proto- 

 plasm around the nucleus and finer peripheral 

 and central processes. 



d. The gustatory organ. 



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

 already been described (B. n. a). 



a. Snip off a bit of mucous membrane from the 

 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- 

 pilla: some (filiform papilla) are pointed at 

 the free end and others (fungiform papilla) 

 flattened. Note the loops which the blood 

 capillaries make in some of the papillae. 



ft. 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 



