PRELIMINARY NOTE ON THE PRESENCE OF A 

 NEW GROUP OF NEURONES IN THE DOR- 

 SAL ROOTS OF THE SPINAL NERVES 

 OF THE WHITE RAT. 



SHINKISHI HATAI. 

 (From the Neurological Laboratory of the University of Chicago. ) 



While the writer was examining a large number of prepara- 

 tions of the spinal cord of the white rat at different ages, in order 

 to determine whether the so-called " Hoffmann's nucleus," de- 

 scribed recently by von Kolliker (" Weitere Beobachtungen ueber 

 die Hoffmannschen Kerne am Mark der Vogel ;" Anat. Anz., Bd. 

 XXI., No. 3 u. 4, 1902), appears in the central nervous system 

 of mammals, his attention was drawn to a group of nerve cells in 

 the dorsal roots of the spinal nerves. 



The spinal cord of the white rat examined does not have an 

 isolated group of efferent neurones in the region where it was 

 found in the spinal cord of birds. Hence the nucleus of Hoff- 

 mann is not present in this animal. A new group of cells was, 

 however, noticed in the dorsal roots, separated from the spinal 

 ganglia and lying between the spinal ganglion and the cord. The 

 shape and structure of the cell-bodies found in this new group 

 coincides with that of the cells in the spinal ganglia, and further, 

 the size of the cells found in this group is approximately similar 

 to that of the cells in the corresponding ganglion. The cell-body 

 is well formed and contains one large nucleus in which one 

 nucleolus generally, or sometimes more than one, is visible. The 

 stainable masses are present in the cytoplasm, showing a char- 

 acteristic arrangement ; the latter substance stains red with eosin 

 with the same intensity as that of the spinal ganglion cells. In 

 every respect the cells which belong to the new group are similar 

 in appearance to the cells of the spinal ganglion. It is easy to 

 see that the cell bodies are surrounded by a connective tissue 

 capsule. In some instances, the capsule is more highly developed 

 than that of the spinal ganglion cells. 



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