HISTOLOGY OF THE FROG 



89 



structure known as the lenticular body (fig. 15, C). At the 

 base of each rod is an oval nucleus surrounded by a very thin 

 sheath of granular protoplasmic matter which is continued inter- 

 nally as a fine fibril ; this probably becomes continuous with, 

 or comes in contact with, a terminal fibril of the optic nerve. 

 Hair-cells from the crista acustica of an ampulla of the ear 



Various forms of sensory epithelium. A, two torked cells from the tongue 

 of the frog ; B, B', two forms of auditory hair cells from the crista 

 acustica of the anterior ampulla of the frog's ear ; C, three rods and a 

 cone from the retina of the frog's eye; D, two olfactory cells, with 

 their epithelial supporting cells from the frog's nose. (All the figures 

 after Haslam in Ecker's "Anatomy of the Frog." Engl. Ed.) 



are shown in fig. 15, B. Each is a pyriform cell, the narrower 

 end turned towards the cavity of the ampulla, and bearing 

 on its truncated free surface a long stiff hair-like process which 

 rests by a broad base on the cell. The opposite broader end 

 of the cell usually appears rounded, but sometimes a fine 

 fibril may be seen springing from it, and this probably 

 becomes continuous with a terminal fibril of the auditory 



