NERVOUS TISSUE. 



101 



FIG. 71. 



only conducting portion of the neurone, while the dendrites are 

 nourishing organs. Most authors, however (Ramon y Cajal, 

 van Gehuchten, Retzius, etc.), are of the opinion that both 

 dendrites and axones have the power of conducting impulses. 

 According to Ramon y Cajal, the dendrites can conduct 

 impulses only toward the cell (cellulipetal), while the axone 

 conducts them only away from the cell 

 (cellulifugal). In this way impulses pass 

 from one neurone to another. 



It is therefore to be observed that all 

 peripheral fibres of the sensory nerves 

 bringing impulses from the outer world to 

 the ganglion cells are dendrites, and such 

 fibres as those of the motor nerves carry- 

 ing impulses out to the muscles are axones. 



On the basis of investigations by 

 newer methods (especially Golgi's) the 

 idea has gained ground that neurones 

 are connected with one another only by 

 contact. But concerning this point there 

 has been much discussion. 



For the last few years the neurone 

 doctrine has been generally accepted 

 i. e., that the nervous system is made up 

 of cells and cell processes forming together units or neurones 

 which combine into systems of fibres and groups of cells. The 

 late work of Apathy, however, throws doubt on the theory in 

 the eyes of many investigators. Apathy finds that direct con- 

 nections exist between ganglion cells, and claims that the 

 nervous system cannot therefore be divided into morphological 

 units (neurones). He makes the last elements of the nervous 

 system not cells, but the so-called neurofibrils, which pass, 

 according to him, without interruption from one cell to another. 

 Even though it is possible to find certain cells joined to others, 

 and fibrils continuous from one to the other, there is still 

 nothing in this to disprove the neurone theory. The neurone 

 doctrine states that the cells and fibres of the nervous system 



Semidiagrammatic repre- 

 sentation of the transition 

 from bipolar to unipolar 

 nerve cells. 



