MORPHOLOGY OF EYE MUSCLE NERVES 37 



ment with Apathy, Held is of the opinion that the solution of 

 the problem of the devolopment of nervous tissue depends 

 primarily upon the demonstration of the place and manner of 

 origin of the neurofibrillar substance. He concludes that this 

 important nervous element is differentiated within the neu- 

 roblasts of His, which are thus the essential nervous cell centers. 

 These results are in harmony with the experimental results 

 of Harrison, Lewis and Burrows. 



Held finds that the first and surest histological characteristic 

 of a cell of neuroblastic tendency lies in the occurrence of a 

 specific network or neuro-reticulum which appears in a cir- 

 cumscribed region of the neuroblast in the vicinity of the nu- 

 cleus. In the course of its development this network undergoes an 

 extraordinary complication and extension of its substance. The 

 observation of the primary appearance of the neuro-reticulum 

 within the neuroblast had previously been made by Besta ( '04) . 



Contrary to the opinion expressed by His, Held affirms that 

 it is not the outflow of protoplasm into a cell process, but the 

 definitely directed growth of a new and special cell substance 

 which originates the first nerve trunks in the embryo. The 

 process is not that the cell produces a protoplasmic elongation 

 of the cell body in which subsequently and secondarily a fibrillar 

 substance appears. On the contrary there are inner changes 

 within the protoplasm of a neuroblast that lead eventually to 

 the differentiation of a neurofibrillar substance which, while 

 primarily of a minimal extension within the fibrillogenous zone 

 of the neuroblast cell, later in the course of its special growth 

 undergoes a mighty extension in the body after it has produced 

 externally the pear-shaped form of neuroblast first observed by 

 His. This fibrillar structure of the neuroblasts is 'neurofi- 

 brillar' in the von Apathy sense of the word. 



Held's conclusions do not agree with those of von Apathy 

 ('98) who holds that the ganglion cells produce no neurofi- 

 brils but are secondarily penetrated by them. According to 

 Apathy, the neurofibrils are produced by other and special 

 cells — the 'nerve cells' — which are not to be confounded or 

 identified with 'ganghon cells.' The 'nerve cells' produce, ac- 



