MAMMALIA — BIRDS— KEPTILES. 



21 



more highly organized. Each consists of an ellipsoidal 

 nucleus surrounded by a thin layer of protoplasm, 

 continued downwards into a fine fibril, which sometimes 

 branches, and which — though this is not clear — probably 

 joins the nervous fibres. The upper process of the 

 protoplasm is a narrow cylinder, in some cases prolonged 

 at the end into a very delicate hair or rod. 



Schwalbe thought he could distinguish in man and 

 the sheep, two kinds of taste-cells — firstly, needle cells, 

 in which the cell appears to terminate in a narrow, 

 brilliant needle, abruptly cut off at the end; and, 

 secondly, staff cells, which are less numerous, shorter, of 

 uniform breadth, and without 

 any terminating needle. It is 

 still unknown whether there are 

 different classes of taste-cells 

 for different tastes, and whether 

 one taste-bud can distinguish 

 more than one taste. 



I know of no detailed de- 

 scription of the organs of taste 

 in birds and reptiles. In the 

 frog the taste-organs are not 

 flasklike, but are flat disks. 

 They occur in hundreds on the 

 tongue and soft palate. These 

 taste-disks are composed of 

 several forms of cells. Those 

 which are supposed to be espe- 

 cially connected with the sense 

 of taste terminate in a fork, sometimes, though rarely, 



Fig. 23. 



Termination of tho 

 nerves of taste in the frog, 

 sliowing the ramifications of 

 the nerve-tibres and their con- 

 nection with the cells of taste 

 (after Engelmann), x 600. 



of three prongs, 

 like beakers. 



The taste-organs of fishes are shaped 



