A HISTORY OF SCIENCE 



experiments. So also did the veteran histologist 

 Kolliker, and soon afterwards all the leaders every- 

 where. The result was a practically unanimous con- 

 firmation of the Spanish histologist's claims, and 

 within a few months after his announcements the 

 old theory of union of nerve cells into an endless 

 mesh- work was completely discarded, and the theory 

 of isolated nerve elements the theory of neurons, 

 as it came to be called was fully established in its 

 place. 



As to how these isolated nerve cells functionate, Dr. 

 Cajal gave the clew from the very first, and his expla- 

 nation has met with universal approval. 



In the modified view, the nerve cell retains its old 

 position as the storehouse of nervous energy. Each of 

 the filaments jutting out from the cell is held, as be- 

 fore, to be indeed a transmitter of impulses, but a trans- 

 mitter that operates intermittently, like a telephone 

 wire that is not always " connected," and, like that wire, 

 the nerve fibril operates by contact and not by con- 

 tinuity. Under proper stimulation the ends of the 

 fibrils reach out, come in contact with other end fibrils 

 of other cells, and conduct their destined impulse. 

 Again they retract, and communication ceases for the 

 time between those particular cells. Meantime, by a 

 different arrangement of the various conductors, differ- 

 ent sets of cells are placed in communication, different 

 associations of nervous impulses induced, different 

 trains of thought engendered. Each fibril when re- 

 tracted becomes a non-conductor, but when extended 

 and in contact with another fibril, or with the body of 

 another cell, it conducts its message as readily as a 



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