290 journal of Comparative Neurology and Psychology. 



in these regions and helps to increase their atrophic appearance. 

 The degeneration of nerve cells results in the disappearance of a 

 certain, apparently variable, number of ventral horn cells and a 

 very considerable and constant number of spinal ganglion cells. 



It has been shown by careful enumeration that after cutting 

 the second cervical nerve of the white rat, one-half of the cells in 

 the corresponding spinal ganglion degenerate and disappear. 

 This reaction is very constant and uniform; in the nine ganglia 

 studied the percentage of variation is no greater than the percent- 

 age of individual variation in the normal ganglia. This is pe- 

 culiar in that many more cells disappear than can be accounted 

 for in terms of medullated fibers cut at the time of the operation; 

 and while it is not possible at present to give a satisfactory ex- 

 planation of the results they point to some as yet unknown 

 relations in the ganglion. 



The number of fibers in the dorsal root is open to much greater 

 variation; but there is on the average a loss of about 17 per cent. 

 The dorsal roots seem more susceptible to the degenerative 

 changes in the young than in adult animals. 



The degeneration of ganglion cells is constant, that of the dorsal 

 root fibers is variable and is much less extensive than would be 

 expected from the number of cells which disappear. This shows 

 that the degeneration in the dorsal roots cannot without some 

 qualification be attributed to the degeneration in the spinal gan- 

 glion. It is hoped that an investigation now in progress will sup- 

 ply the necessary data for the interpretation of these results. 



Contrary to the usual conception, the degeneration of fibers and 

 cells was not progressive; it had been completed before the end 

 of the first two months, after which there was no further change. 



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BtRARD. Bulletins de la Societe anatomique de Paris. No. 3. May, 1829. 



Berg. Contribution a Tetude des nerfs et de la moelle chez les amputes. Thesis, Paris. 1896. Cited 



after Switalski. 

 BiEDL, A. Ueber das histologische Verhalten der peripheren Nerven und ihrer Centren nach der 



Durchschneidung. Wiener Klin. Wochenschr. Bd. 10, p. 389. 1897. 

 Braeunig, Karl. Ueber Chromatolyse in den Vorderhornzellen des Riickenmarkes. Arch. f. Anat. 



u. Phys., Phys. Abth., p. 251. 1903. 

 Braeunig, Karl. Ueber Degenerationsvorgange im motorischen Teleneuron nach Durchschneidung 



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