PROPERTIES OF THE NERVE CELL. 



123 



far as conduction is concerned, shows a definite polarity, the con- 

 duction in the dendrites being cellulipetal, in the axons, cellulifugal. 



The neuron doctrine, so far as the name at least is concerned, dates from 

 a general paper by Waldeyer,* in which the newer work up to that time was 

 summarized. The main facts upon which the conception rests were furnished 

 by His (1886), to whom we owe the generally accepted belief that the nerve 

 fiber (axis cylinder) is an outgrowth from the cell, and secondly by Golgi, 

 Cajal, and a host of other workers, who, by means of the new method of Golgi, 

 demonstrated the wealth of branches of the nerve cells, particularly of the 

 dendrites, and the mode of connection of one nerve unit with another. The 

 view that these units are anatomically independent and on the embryological 



Fig. 54. Motor cell, anterior horn of gray matter of cord. From human fetus (Lenhoa- 

 sek) : * marks the axon ; the other branches are dendrites. 



side are derived each from a single epiblastic cell (neuroblast) has proved 

 acceptable and most helpful; but the validity of this hypothesis is again 

 called into question. As was stated on p. 119, Bethe has shown apparently 

 that in young animals the nuclei of the neurilemmal sheath may regenerate 

 a new nerve fiber containing axis cylinder and myelin sheath, and this fact 

 at once brings into question the hitherto accepted belief that the axis cylin- 

 der can be formed only as an outgrowth from a nerve cell. In fact, it indi- 

 cates strongly the probability of an older view, according to which the axis 

 cylinder is formed by the fusion of a series of cells whose origin is the same 

 as those represented" by the nuclei of the neurilemma. Some histologists 

 Ap&thy, Bethe, Nissl have also attacked the most fundamental feature of 

 the neuron doctrine, the view, namely, that each neuron represents an inde- 



*"Deut. med. Wochenschrift," 1891, p. 50. 



