Meyer, Data of Modem Nciuvlogy. 127 



can exist except as a process of a nerve cell. AH this is em- 

 phatically denied by all writers outside of England. Prof. C. 

 Hnbcr, of Michigan University, who has studied the question 

 with Prof. Howell, and to whom a similar statement had been 

 ascribed, writes me that he has seen no evidence in favor of 

 such assumptions. In connection with this we must mention 

 a discussion which was carried on in the camp of morphologists, 

 and which is never referred to in the discussions concerning the 

 neurone theory. The most important contribution is undoubt- 

 edly one of /. Beard, the histogenesis of nerve\ A. Dohrn, 

 the head of the Zoological Station at Naples, published memoirs 

 on this subject which fully supported Beard's own way of see- 

 ing things. Dohrn (quoted in Beard's article) says : 



"Thus we have the picture of a nerve such as is found 

 typically everywhere. The nuclei are Schwann's nuclei, the 

 light shining cylinders are the axis cylinders, the plasma is the 

 soil of Schwann's and of the medullary sheath appearing later. 

 These four elements constituting the typical nerve, are exclu- 

 sively products of ectoderm cells disposed in chains for the for- 

 mation of individual fibers." Beard says (p, 295): "These 

 chains (i. e. their nuclei) proceed to secrete, from before back- 

 wards as fast as they are formed, nerve fibrils or axis cylinders 

 outside of themselves, and each Hnear row secretes one axis 

 cylinder." In the case of the motor nerves "the chains of 

 cells leave the cord in a manner often described, and finally de- 

 tailed by Dohrn in more than one publication. The blunted 

 peripheral termination of the chain becomes applied to the 

 muscle plate, and, with great certainty I can repeat what I have 

 more than once stated, that the terminal end-plates of muscle 

 and of the electric organs are formed from the wandering of 

 such cdls along v/ith the nerve-forming cells seiisri strido from 

 the anterior horn to the terminal region. These terminal cells 

 imist be regarded as ganglionic in character. In connection with 

 these chains of cells the formation of nerve takes place just as 

 described in the above." He further draws attention to the 



1 Anatomischer Anzeiger, VII, pp. 290-302. 



