238 bulletin: museum of comparative zoology. 



12. Sections parallel to the long axis of the sense cells demonstrate 

 the existence of free-ending axis cylinders. 



13. Sections parallel, or nearly so, to the surface of the epithelium 

 demonstrate that the nervous material is intercellular. 



VII. General Discussion and Conclusions. 



From the foregoing account it appears that in the ear, at least, we 

 have a portion of the peripheral system in which the conditions are 

 such as to furnish strong anatomical evidence in support of the neurone 

 theory. The absence of anastomosis between different axis cylinders, 

 the distinctness of the sense cells, and the free terminations of the axis 

 cylinders, support the validity of that view. Though different authors 

 have declared in a general way that anastomosis does occur, I am not 

 aware that any investigator has maintained that the neurofibrillae of 

 one axis cylinder are continuous with those of another, which I believe 

 to be essential to a true condition of anastomosis. Retzius (:05'^), 

 who has given this subject more study than any other investigator, 

 states that he has never seen cases of true anastomosis. 



The cjuestion whether free terminations exist or not depends upon 

 what is meant by that term. Bethe and other adherents of the fibrillar 

 theory oppose the doctrine of free nerve terminations. Dogiel (:05), 

 who holds a modified form of the neurone theory, also disbelieves in 

 their existence. The opposition is based upon the affirmed existence 

 of peripheral networks of neurofibrillae. Thus Szymonowicz ('96) 

 has described such closed terminal structures in Grandry's corpuscles. 

 Dogiel (:04) has recorded similar structures in the Herbst bodies. 

 I have already (p. 217) stated Kolmer's view, that the fibrillae of the 

 eighth nerve have no free ends, but turn back at the periphery, forming 

 loops, rings, or networks. If by free nerve terminations is meant the 

 free ending of the neurofibrillae, and the maintenance of their indi- 

 viduality to the periphery without anastomosis with one another, my 

 preparations do not furnish conclusive evidence in the matter. But 

 if by free ending is meant the maintenance of the individuality of axis 

 cylinders, or branches of axis cylinders, to the periphery without 

 anastomosis with one another or with other elements, — such axis 

 cylinders being composed of a greater or smaller number of neurofi- 

 brillae, — I cannot doubt that they are abundant in the region which 

 I have studied. It is in this latter sense that the term is used by 

 Retzius and other neuronists. Networks of neurofibrillae such as 



