272 ^Journal of Comparative Neurology and Psychology. 



KosTER ('03), having cut the sciatic immediately after its exit 

 from the vertebral canal in cats, dogs and rabbits, found that all 

 the spinal ganglion cells presented alterations of their tigroid 

 bodies. Only a part of these cells suffered complete degeneration 

 and this occurred for the most part after the 284th day. The 

 phase of repair followed the chromatolysis in a large part of the 

 cells and it was particularly in the large cells that the restoration 

 of the tigroid substance w^as most evident. The cells that sur- 

 vived had undergone considerable atrophy. Kleist ( 04) made 

 his experiments on half-grown cats and rabbits, cutting some of 

 the upper cervical or lower thoracic nerves. After from three to 

 six months a large proportion of the spinal ganglion cells (esti- 

 mated at 33 per cent.) had disintegrated and the remaining cells 

 had undergone a marked atrophy. 



The practical bearing of this problem has been indicated by 

 ScHAFFER in his Text-book of Physiology: "If the observation 

 of VAN Gehuchten upou the nerve cells of the vagal ganglion 

 after section of their peripheral fibers is correct, and is a phenom- 

 enon of general occurrence, it is difficult to see how the sensory 

 fibers regenerate. Restoration of function in such cases may, 

 perhaps, often be explained by the ingrowth of sensory nerve fibers 

 from adjacent areas of distribution." 



2. Observations on the Second Cervical Nerve of the White Rat. 



The unsatisfactory character of the data on the changes in the 

 spinal ganglia, resulting from the section of the associated nerves, 

 emphasizes the necessity of some further investigation along this 

 line, and in the experiments now to be described special attention 

 was given to determining the extent of cell destruction in the gan- 

 glion. It is necessary, by way of preface, to state a few of the essen- 

 tial points concerning the relation of the spinal ganglion to the 

 afferent fibers of the nerve and dorsal root. We may safely accept 

 as the essential element, the unipolar cell with its T-shaped fiber, 

 despite the fact that Nissl ('03) has called attention to some facts 

 that point to another view. Nevertheless there are many cells in 

 the ganglion which are not connected with medullated fibers in 

 either the nerve or dorsal root, since enumerations show that the 

 number of nerve cells in the ganglion far exceeds that of the med- 

 ullated fibers in the root (Hatai '02), and by nearly as large an 

 amount the number of medullated afferent fibers in the peripheral 



