The Journal of 



Comparative Neurology and Psychology 



Volume XVIII APRIL, 1908 Number 2 



THE ARCHITECTURAL RELATIONS OF THE AFFER- 

 ENT ELEMENTS ENTERING INTO THE FORMA- 

 TION OF THE SPINAL NERVES. 



BY 



S. WALTER RANSON, PH.D., M.D. 



{From the Anatomical Laboratory of the University of Chicago.) 

 With One Figure. 



INTRODUCTION. 



Some rather surprising observations are recorded in a paper 

 recently published on "Retrograde degeneration in the spinal 

 nerves" (Ranson '06). 



It was found that after the division of a nerve, containing 1500 

 medullated afferent fibers, there occurred a complete degeneration 

 of 4500 spinal ganglion cells and that this was accompanied by 

 little or no degeneration of the dorsal roots. It was at once appar- 

 ent that these results would be very difficult to explain on the 

 basis of the usual conception of the spinal ganglion. Accord- 

 ingly, the literature dealing with the architecture of the spinal 

 nerves and of their dorsal root ganglia has been carefully reviewed 

 in the hope of finding some observations that would be of assist- 

 ance in interpreting these facts. 



Another reason for presenting the normal relation of the sensory 

 elements of the spinal nerves is the fact that in order to obtain a 

 norm for the second cervical nerve of the white rat (the nerve 

 studied in this series of experiments) it was necessary to make a 

 study of the numerical relations in that nerve and these obser- 

 vations have some value from the anatomical point of view. 



