MULLENIX: EIGHTH CRANIAL NERVE. 239 



have been described by Dogiel, Szymonowicz, and Kolmer are in 

 ])erfect accord with Apathy's theory, but they are in no sense irrecon- 

 cilable with the neurone theory. Likewise, the free ending of axis 

 cylinders, while it seems to be emphasized principally by neuronists, 

 is not at all incompatible with the fibrillar theory. The confusion in 

 the matter seems to result chiefly from the fact of the different points 

 of view occupied by the fibrillists and the neuronists. 



The adherents of the neurone theory, upon the basis of important 

 anatomical, embryological, and degeneration evidence, look upon the 

 ganglion cell, dendrite, and axis cylinder as together constituting the 

 structural unit of the nervous system. The existence of the neuro- 

 fibrillae has long been recognized, but modern neuronists regard them 

 as constituent parts of larger morphological units (Parker, :00, Collins, 

 :06). Apathy and his followers, on the other hand, magnify the 

 importance of the neurofibrillae and attach less significance to the more 

 complex structure which is known as the neurone. Apathy represents 

 the neurofibrillae as structures which maintain their individuality 

 in the nerve fibre, losing their identity only in three localities, viz., in 

 the neuropile, the ganglion cell, and the innervated organ, — sense 

 cell, muscle fibre, or gland cell. He represents the sensory fibrillae as 

 anastomosing in the neuropile to form an "Elementargitter," out of 

 which larger fibrillae are assembled, which make their way to muscle 

 fibres as motor fibrillae. From this conception Bethe draws the 

 deduction that the neurofibrillae of the receptor organs extend without 

 interruption to the neuropile, and from there to the motor ganglion 

 cell, still without interruption, and are continued in the eft'erent nerve 

 as motor fibrillae which make their way to the terminal organ, still 

 without interruption. In other words, Bethe conceives that in the 

 neurofibrillae there exists a continuous bridge between receptor and 

 motor elements. 



It is not my purpose to undertake a criticism of Apathy's view, 

 further than to remark that, while his conception is in some respects 

 very plausible, there is much in it that is extremely hypothetical. 

 To assign to the neurofibrillae, exclusively, the power of conducting 

 nerve impulses is to make an assumption which is not supported by 

 evidence. 



I have given this resume of Apathy's fibrillar theory in order to 

 prepare the w^ay for a more critical consideration of the extracellular 

 networks and the intracellular nervous structures which have been 

 described by Kolmer and by Bielschowsky und Briihl. These in- 

 vestigators are agreed in their account of pericellular networks. In 

 regard to endocellular nervous structures they differ. 



