36 Journal of Comparative Neurology. 



the brilliant work of Gehuchten had afforded proof of the same 

 thing, but the suggestion was of course inevitable that we have 

 in the lower forms a permanent retention of cells in the skin 

 which in higher types have tended to become concentrated in 

 the central organs. What more natural, however, than that 

 this concentration should be incomplete, especially where these 

 cells have have acquired a specific sensory function. When the 

 application of the Golgi and methylene blue methods revealed 

 the fact that there is a most complicated set of free endings in 

 the skin and that in many cases where a nervous continuity had 

 been described there is simply a secondary apposition of a den- 

 drite to preexisting non-nervous cells it was inevitable that the 

 existence of cellular nerve endings should be discredited en- 

 tirely. It is true that the greater part of the sensory prota are 

 collected in the spinal and cranial ganglia and seem to prolifer- 

 ate thence to the periphery; but in various regions, particularly 

 of the head, these ganglia never concentrate in a neural ridge 

 but retain their original place in the neighborhood of pharyn- 

 geal clefts and the like and the possibility must be allowed that 

 other cell-clusters elsewhere may have done the same. How- 

 ever, there is another possibility to be considered ; namely, that 

 the terminal portion of the peripherally proliferating nerve fiber 

 may under certain circumstances develop a specialized terminal 

 dendrite. When the nerve is in process of developing the sub- 

 division of the distal member is repeated progressively until 

 the definite terminus is reached and then the extreme element 

 is charged with the function of adapting itself to the conditions 

 there prevailing. In the case of the motor ending, even the 

 careful researches of Huber and De Witt do not finally dispose 

 of the question as to the origin of the end-structures. We may 

 interpret them as follows : when the fiber reaches the muscle 

 its terminal element, together with the nucleus, applies itself to 

 the surface of the latter and prior to the formation of the mus- 

 cle-sheath, proliferation goes on in a less regular way than dur- 

 ing the development of the nerve itself, in this way is formed 

 the " sole," which would, accordingly, be of a nervous nature. 

 On the other hand, it is possible that the nerve on entering the 



