NOTE ON THE STRUCTURE AND THE DEVELOP- 

 MENT OF NERVOUS ELEMENTS. 



By Paul Mitrophanow, 



Professor hi the University of Warsmv. 



The question of the origin of the nerves, of their structure, 

 and the character of the nervous endings in the sense organs 

 was studied during the last year with special assiduity. In a 

 recent session of the biological section of the Society of Natur- 

 alists in Warsaw I took occasion to indicate the investigations 

 of Lenhossek ^ and Dohrn," which seemed to alter essentially 

 the opinions respecting the peripheral nervous system. A very 

 important fact in these investigations is the part taken in the 

 formation of the elements of the nervous system by the cutane- 

 ous integument — embryonic in vertebrates, but even in adults 

 of invertebrates. But while Lenhossek sought simply to regard 

 the cutaneous integument as the birth place of the sensory 

 nervous cells and fibres, Dohrn attempted a revision of the 

 doctrine of the nervous elements by demonstrating that the 

 nervous fibre is a formation of many cells, that it is composed 

 of a row of ectodermic cells, every one of which gives to the 

 fibre its constituent parts: the axis cylinder, the envelops and 

 the nucleus. He calls these cells nervous, wishing to distin- 

 guish them from the ganglionic ones which, according to his 

 opinion, do not take any part in the formation of the nervous 

 fibre, that is to say, of the axis cylinder, and are in connection 

 with it only by contact. 



Sometime since ^ I exposed the weak sides of Dohrn's po- 

 sition and the possible explanation of the facts from which he 

 developed it. It was natural that I should expect a more par- 



^M. Lenhossek. Ursprung, Verlauf und Endigung der Sensibeln Nerven - 

 fasern bei Lumbricus. Arch. f. mikr. Anat. XXXIX. 1892. 



^ A. Dohrn. Nervenfaser und Ganglienzelle. Mittheiltingen aus d. Zool. 

 Station zu Neapel. X, 1891. 



' P. MjTROPHANOW. Suggestions on the development of vertebrates. 1S92. 



