CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE, 

 UNDER THE DIRECTION OF E. L. MARK. — No. 122. 



THE DEVELOPMENT AND FUNCTION OF REISSNER'S 



FIBRE AND ITS CELLULAR CONNECTIONS. 



A PRELIMINARY PAPER. 



By Porter Edward Sargent. 



Presented by E. L. Mark, March 13, 1901. Received March 15, 1901. 



In a recent number of the Anatomischer Anzeiger (Bd. XVII. pp. 33- 

 44) I have described the occurrence of Reissuer's fibre in the canalis 

 centralis of vertebrates, and I there promised the early appearance of a 

 paper on its development. My further researches on its development 

 and cellular connections have led to the discovery of a highly specialized 

 apparatus, of vrhich the so-called fibre forms a part. The subject has 

 developed much larger aspects than was anticipated, and the consequent 

 delay in the public;ition of my complete results makes necessary a fur- 

 ther preliminary paper. 



As described in the previous paper, Reissner's fibre lies in the cere- 

 bro-spinal fluid ; it extends through the whole length of the canalis 

 centralis and the brain ventricles to the anterior portion of the optic 

 lobes, where it passes into the brain tissues; it gives off throughout the 

 posterior portion of its course fine branches, which enter the tissue of 

 the spinal cord. 



In the present paper I hope to show briefly that there is normally in 

 the central nervous .system of all vertebrates a highly specialized appara- 

 tus, the cells of whicli lie in the optic lobes and send their axons into 

 the optic ventricle and the central canal to form the so-called Reissner's 

 fibre. I have investigated the occurrence of this apparatus in upwards 

 of one hundred species, representing all the principal classes and sub- 

 classes of vertebrates. The development has been studied in about 

 twenty different species, and has been more or less completely worked 

 out in representatives of all the chief groups of vertebrates. In this 

 paper I shall describe the apparatus and its development in a few char- 



