248 Journal of Comparative Neurology. 



of Duval's evidence. Duval closes this paper with the statement of a 

 fresh hypothesis which he calls the theory of nervi-nervorum. 



Deyber's paper (30) also appeared in 1898. It appeared but two 

 years after the thesis of Pupin. The publication of a second work on 

 the same subject within so short a time was called out by the researches 

 mentioned above, which contain the so-called direct proofs of the the- 

 ory of Duval. One point pecuhar to Deyber's treatment is his defence 

 of the theory of contiguity against certain recent attempts to reestab- 

 hsh a doctrine of the continuity of the nerve elements, as exemplified 

 by Dogiel. Duval's theory rests, of course, upon the assumption of the 

 correctness of the current theory of the anatomic independence of the 

 neurones. Deyber also makes a reply to Kolliker's criticism of Duval's 

 theory. Deyber's paper winds up, like that of Duval, by referring to the 

 large acceptance which the theory of amoeboid movements has had 

 with histologists. Bechterew (11), van Gehuchten (39 and 50), Azou- 

 lay (6 and 7), Regnault (90), Le Dantec (56), Fleury (35 and 36) 

 Richet (23) Soukhanoff (102 and 103), Querton (84), Loeb (60) all 

 take a more or less favorable attitude toward it. 



It may be seen, thus, from the foregoing series of papers, to what 

 an extent this conception of the amoeboid contractiUty and expansibil- 

 ity of the neurone has penetrated the sphere of histology of the ner- 

 vous system. The question now arises as to the interpretation of the 

 evidence which has been presented. The aim has been simply to 

 outline in a general way the historical development of the doctrine by 

 reference to the chief papers which have appeared on the subject. 

 Only articles which have taken up the subject with more or less full- 

 ness have been referred to here. Other articles will be referred to in 

 what follows, which is a critical examination of the data presented. 



II. Critical. 



We may follow Duval and Deyber and group the evidence into 

 two general divisions, first, proofs by analogy, and second, direct 

 proofs. 



Before taking the first line of evidence, two pomts may be sum- 

 marily disposed of — the supposed evidence from Wiedersheim's observa- 

 tions, and the argument from Tanzi. These cannot be proofs of the 

 theory of amoeboid movement in any sense, since they are irrelevant 

 to the point in question. Wiedersheim's observations (109) on the cere- 

 bral ganglion of Leptodora hyalina do not concern changes of the 

 nerve cell as a whole, which alone can be characterized as amoeboid, 

 but relate only to certain inclusions in the nerve cell which undergo 



