THE TISSUES 



t A 



> o 



stantaneous ; it takes an appreciable and measurable Nerve cells 

 time. Formerly it was supposed that the nerve fibers, 

 which seem to present no 

 cellular structure, were not 

 parts of cells. We now 

 know that the nerve cell, 

 with its nucleus, is pro- 

 longed into fiber-like exten- 

 sions, reminding us of the 

 pseudopodia of the amiba, 

 but vastly longer, and per- 

 manent. Bundles of these 

 fiber-like filaments consti- 

 tute the nerves. The gen- 

 eral property of irritability 

 is here greatly accentuated, 

 and the impulse is capable 

 of being conveyed to other 

 kinds of cells, which act in 

 consequence of it. So far 

 we seem to be dealing with 

 nothing more than an ex- 

 treme modification of prim- of secretions. A represents the simplest 

 itive functions, but when case ' in which tluree ceUs ( shaded ) are 



capable of secreting some substance, 



we come to regard mental which is poured out on to the surface o 

 phenomena, especially as the bod y- In B the s land cells secrete 



r i . into a pocket or tube, which is capable 



found in man, we enter upon of holding the material until it is 



a new field. The power of wanted, as in the case of the saliva or 

 i ^i the secretion of the stomach (gastric 



memory may be theoreti- juice) . This makes it ^Me to furnish 



Cally explained as analogous at a given moment much more of the 



to that of the phonograph ; secre f d * 5t ce ^ han l T he c f ls cox f 



J ' supply without notice. In plants the 



a path Of disturbance lias gland cells are often situated on a 



left its record in the brain. knob or P rominen ce or at the end of a 



TTT, . hairlike structure, thus reversing the 



When We Come tO COnSClOUS- structure of the tubular gland. 



FIG. 



section. 



Drawing by R. Weber 

 Diagrams of gland cells, in 

 The arrows mark the outflow 



