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\vliicli become more and more Blender ;is they branch until 

 their ultimate subdivisions defy observation. Each nerve- 

 crll, as a rule, has many of these brush-like extension-, 

 and since other cells are near at hand the processes inter- 

 lace in a bewildering fashion. A recent writer has likened 

 the resulting situation to that prevailing in a forest where 

 the branches of each tree penetrate among those of its 

 neighbors. Looking among the foliage from a little dis- 

 tance one cannot tell to which tree individual twigs belong. 



Keeping for the moment the illustration just introduced, 

 it may be said that the observer could hardly tell whether 

 the ends of the small branches ended freely or ran together. 

 His information would enable him to decide that each 

 tree is really quite without connection with any other. 

 but he might not be able to determine this by his distant 

 inspection. This represents with entire justice the diffi- 

 culties encountered by workers who have tried to inter- 

 pret the appearance of the gray matter. They have not 

 been able to agree as to whether the processes of one nerve- 

 cell are continuous with those of others or whether they 

 merely mingle closely. Fortunately, the physiology of 

 the nervous tissues can be discussed without the adoption 

 of one view to the exclusion of the other. The prime fact 

 has to be accepted that effects are produced by certain 

 cells upon their neighbors. 



A term which it is most important to understand is 

 ^!//nij>s, . A synapse is said to exist wherever the branch- 

 ing processes of a nerve-cell transmit stimulating energy 

 to the processes of a second unit. If there is no con- 

 tinuity between t he two, the synapse is a place of contact 

 or of do>e approach. If the adjacent units of the gray 

 matter are really bound together, the synapse is the region 

 of the finest subdivision of the protoplasmic bonds between 

 them. If we speak physiologically, the synapse is a 

 functional junction; it is not absolutely necessary t<. 

 decide whether it is an anatomic junction. One doctrine 

 implicitly held with reference to the synapse is that trans- 

 mission aero-- it can take place in only one direction. 



