MOTOR NERVE-ENDING 



193 



or tactile cell of a vertebrate, without any processes and with its discharg- 

 ing surface directly in contact with the afferent or perceptory end-brush 

 of a fiber leading to 

 the central nervous 

 system (see Fig. 198). 

 The most fre- 

 quent type is exem- 

 plified, perhaps, by 

 the connection estab- 

 lished between the 

 discharging end of a 

 branch of a stellate 

 nerve cell of the cer- 

 ebellum with the cell 

 body of one of the 

 Purkinje cells in the 

 same organ. This 

 relation is shown in 

 Figure 169, stell. end., 

 but its value as an 

 example is impaired 

 by the fact that the 

 cell-body surface of 

 the Purkinje cell is 



olf. 



FIG. 170. Portion of a section of the olfactory bulb of man. 

 Stained with nitrate of silver to show the perceptory endings of 

 mitral cells (mi.c.) in contact with the stimulatory end-organs of 

 the olfactory cells, which are not shown in the figure, but whose 

 efferent fibers enter the figure from the sides (olf.fi.). The oval 

 area in which this meeting takes place is called an olfactory 

 glomerulus (olf.gl.). (From HUBER after GOLGI and CAJAL.) 



not its main per- 

 ceptory surface, this 

 being represented by 



the widely branching dendrites, which furnish us with an example 

 of another and more typical variation of the same kind of connec- 

 tion as that mentioned last. This is the contact of the discharging 

 end of a nerve fiber (here the cerebellar climbing fiber) with the percep- 

 tory processes of the Purkinje cell (Fig. 169, cl.fi.}. The finely branched 

 fibers of the two end -organs lie parallel with one another and in a_contact 

 that is sufficiently extensive and intimate to permit of the nerve impulse 

 being transferred from one to the other. Thus, a neuron may have two 

 perceptory surfaces. 



A last example of such a connection is shown by the mingling of the 

 discharging tclodendron of an olfactory nerve cell of a mammal with 

 the perceptory branches on the end of an afferent fiber leading to one of 

 the mitral cells of the olfactory lobe of the brain (Fig. 170). 



The discharging end-organs of nerves that serve to stimulate muscle 

 fibers into motion are well known,. and two or three examples will give a 

 clear conception of their structure. The simplest form is undoubtedly 



