128 Journal of Comparative Neurology. 



views of Vignal who considers the nuclei of Ranvier's nodes as 

 mesoblastic, but shows that they are concerned in the lengthen- 

 ing of the nerve, and that to this end they give origin to inter- 

 calary segments. 



DoJtni himself (Anatomischer Anzeiger, VII, pp. 348-351) 

 practically defeated Beard's view by stating that he is now con- 

 vinced of the terminal growth of the axis cylinder in the sense 

 of His ; and that the cells of Schwann's sheath were mesoblast- 

 ic ; that he had seen fibrils develop independently beyond the 

 "chain of cells ; " which would corroborate the neurone the- 

 ory. Beard, as far as I am aware, has not given up his hetero- 

 dox view as Dohrn did ; I give it therefore a place in this sum- 

 mary as a possible, though not probable, objection to the neu- 

 rone theory. 



Held s recent finding concerning the concrescence of nerve 

 fiber terminations and cells (instead of simple contact) is a very 

 vital objection to certain hasty conceptions of the neurone theory. 

 The facts observed by him are the following: In the new born dog 

 there is in the trapezoid nucleus a distinct limiting line where 

 the end-brushes of a neurite and the protoplasmic body of the 

 cell meet, such as we find wherever two different substances 

 come into contact with each other. In the dog nine days old, 

 however, this limiting line has disappeared and it is impos- 

 sible to make out a boundary between the end-brushes of 

 the other cell and the cell protoplasm itself. This speaks very 

 strongly in favor of actual concrescence and not mere contact. 

 It is evident that the growth of the cell processes becomes by 

 no means more intricate on ground of this observation. The 

 branches divide and those which find definite connection with 

 other cells become fixed, the others remain free. The review 

 in the Zeitschrift fiir Hynotismus says nothing of other anasto- 

 moses [see however our own summary in a later part of other 

 discussions]. Fundamental principles, especially the axiom of 

 the cellular theory, are just as easily understood if we have to 

 admit this observation, as a fact. The fatal blow hits merely 

 the hypothesis of the contractility of the nerve elements which 

 has been exploited for the explanation of sleep and kindred 



