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An Experimental Investigation on the Function of 

 Reissner's Fibre. 



By 

 George E. Nicholls, B.Sc, A.R.CSc, F.L.S., 



Professor of Biology at Agra College {Universitu of Allahabad), India. 



Some fifty years ago a German investigator, Reissner, discovered 

 h/ing freely in the central canal of the spinal cord of the lamprey a very 

 fine cylindrical rod, which he supposed, notwithstanding its unusual 

 situation, to be a delicate nerve fibre. He failed, however, to learn 

 anything concerning its connection with the central nervous system, 

 and his discovery, although confirmed, seems to have attracted but 

 little attention. The few observers who have since that time recorded 

 observations upon Reissner's fibre were almost all agreed that it was 

 to be looked upon merely as an artifact produced by the coagulation 

 of the cerebro-spinal fluid by the action of the fixing reagents employed. 



In the early years of the present century, however, Sargent 

 (1900-1904) took up the study of this fibre of Reissner and announced 

 that he found it to be a nerve tract which formed a direct connection 

 between the optic centre in the mid-brain and the musculature, and 

 permitted, he believed, of a quicker response to optic stimuli than 

 was possible through the ordinary spinal tracts. He claimed to have 

 obtained experimental confirmation for this theory, by observations 

 made upon elasmobranchs, in which he had broken the continuity of 

 the fibre, declaring that he could detect an appreciable slowing in the 

 passage of optical stimuli in the subjects of his experiments as 

 exhibited by their failure to quickly avoid obstacles placed un- 

 expectedly in their path. 



My own observations upon Reissner's fibre and related structures 

 in the central nervous system, which were begun in 1907 and have 

 continued until the present time, while establishing beyond question 

 the fact that the fibre is really a preformed structure,* have at the 

 same time shown conclusively that it is not a nerve fibre or a nerve 

 tract. 



I have been able to demouBtrate that the fibre takes its origin from 

 an extraordinary epithelial organ which lies beneath the posterior 



* Edinger, as recently as 1908, had affirmed tliat it was merely an artifact. 



