I 72 Journal of Comparative Neurology and PsycJiology. 



T/ic Ground Substance and Ncurofibrillae. 



The challenge which came to the neurone theory through the 

 works of Apathy and Bethe has awakened new interest in the finer 

 structure of the cytoplasm of the nerve cell. That there are structures 

 in the properly fixed and stained neurone, especially of invertebrates, 

 which accord with the neurofibrillae of these authors can no longer be 

 doubted. But the exact relation which these fibrillae hold to the pro- 

 toplasm of the living cell, to the inter-relation of neurones, and, there- 

 fore, to the conduction paths of the nervous system, is not satisfactorily 

 explained. Is the neurofibril a protoplasmic thread or is it a derived 

 substance of the protoplasm as Pugnat and others argue? If it is a 

 derived substance, it may well pass beyond the limits of the cell and 

 form extra-cellular nets in the neuropil, as Bethe and Apathy and 

 their followers describe. But if the fibril is protoplasmic its nature ex- 

 cludes the possibility of such nets since the limits of the cell would 

 coincide with the limits of the protoplasm. But if the fibril be proto- 

 plasmic, are there stuctural features of the cytoplasm by which the 

 origin, development and final behavior of the fibril can be explained? 

 Towards the answer of such leading questions, some of the following 

 works contribute in a positive manner. 



Holmgren ('99), in his monograph upon the spinal ganglion cells 

 of Lophius, does not commit himself to a definite statement regarding 

 the ultimate structure of the cytoplasm. He describes however, a cer- 

 tain radial apjiearance about the nucleolus in its migration from the 

 nucleus into the cytoplasm which he considers suggestive of the alve- 

 olar structure. Yet his figures and descrij^tions in general do not 

 seem to sustain this interpretation throughout. In his beautifully ex- 

 ecuted drawings (Taf IX-X, Fig. 3) he represents the cone of origin 

 as marked with stripes which are directed from the axone into the 

 cell body. In the more distal part of the cone these stripes seem to 

 form elongated and very narrow meshes. As the structure recedes 

 into the cell body the meshes become shorter and broader, and es- 

 pecially is this true in the peripheral region of the cell where the 

 meshes become very irregular in shape and size. Though Holmgren 

 does not discuss this structure in detail as related to the structure of 

 the cytoplasm his figures are strongly suggestive of the cytoplasmic 

 reticulum as described by Hatai and others. 



In a later work upon the structure of the nerve cell Holmgren 

 ('00) finds more positive data on this feature of the neurone. 

 He demonstrates a fibrillar structure which he considers identical with 

 the fibrillar substnnce of Flemming. The fibrillae of the cytoplasm are 



