ON THE HISTOLOGICAL STRUCTURE OF THE 

 MEDULLA OF PETROMYZON. 



J. David, Ph.D., Berlin. 



In the course of my investigations with the new methods of 

 Golgi and the modification used by Ramon y Cajal, on the 

 central nervous system of various vertebrates, I found that the 

 nerve fibres in the brain and the spinal cord of Petromyzon 

 stained especially well. 



Nafisen,^ in his investigations upon the central nervous 

 system of vertebrates, makes mention of the structure of the 

 medulla of Myxine glatinosa; he demonstrated with the silver 

 method multipolar cells possessing one nervous and several, 

 three or four, protoplasmic processes, the latter extending 

 toward the surface and ending in little enlargements. The ner- 

 vous processes belong to both types described by Golgi. 



This method however is in Petromyzon more valuable in 

 the results it gives in the way of showing the course and distri- 

 bution of the nerve fibres, which are stained much more clearly 

 than the body of the cells. The few of these latter I saw in P. 

 fluviatilis, are found on each side of the central canal, near the 

 median line, they seemed more numerous in the anterior part of 

 the medulla, Fig. i and 2. These cells have been described by 

 Reissner (MuUer's Archiv. p. 545), Ahlborn (Zeitschr. f. wiss. 

 Zool. 1883); also by Retzius, in his Biologische Untersuchungen, 

 II Folge, 1 89 1. The latter author used the methyl blue method 

 of Ehrlich and obtained good results upon cells and fibres. 

 He gives also one cut showing the results of the Golgi method 

 in Myxine. 



The processes of these cells pass into the fasciculi longitudi- 

 nales into the ventral nerve roots, and also into the white commis- 

 sure. The protoplasmic processes pass into the superior, lateral 

 and inferior part, and penetrate also into the white substance. 

 The indistinct separation of the grey and white matter, as also the 



IBergens Museums Aarsbereting, 1886. 



