204 THOMPSON YATES LABORATORIES REPORT 
IVth lumbar segment. So also in experimental amputations at the thigh and shoulder-joints in 
young Dogs, Homen [loc. cit.) notes that the diminution in the number of cells on the side of the 
lesion was limited to Vllltli, Vllth, and Vlth post-thoracic segments in the lower limb, to the 
first dorsal and Vlllth and Vllth cervical in the case of the upper limb. 
These cases of amputation show the final results in the several spinal segments which 
follow interference with a motor nerve cell (a) by destruction of its axon, (h) by cutting off the 
afferent impulses, and they show that the atrophy is not uniformly proportional to the extent of 
the lesion. 
At tliis point it is necessary to refer again to some observations to be described in tlie 
second part of this paper, viz., that after division of an anterior root, changes are found in all the 
cells within a very short time. 
At present I have no personal knowledge of the ultimate fate of these cells, assuming that, 
after amputation of a thigh, for example, and consequent cutting of all the axons of the cells of the 
various spinal segments connected with the muscles of tlie limb, and initial structural alteration 
occurs in these cells, we have to explain why the final result should be practically limited (as far as 
mere diminution in number) to the postero-external group and to certain segments. The 
explanation why certain cells are more vulnerable is to be found I think in their special 
dependence on the integrity of the afferent impulses; and I wish to emphasize that the changes 
described as occurring after section of the posterior roots are of a very different type to those which 
follow division of an anterior root. They are much more intense, the process of chromatolysis 
has advanced further, and in many cases to such a degree that all trace of the chromatic bodies is 
absent and the nucleus has disappeared. Such cells will probably ultimately atrophy and become 
incapable of recognition. 
11. ON THE CHANGES THAT OCCUR IN A NERVE CELL AFTER 
DIVISION OF ITS AXON 
That a relation exists between the structure of a nerve cell and the integrity of its axon is 
shown by evidence of three kinds. 
(i) In newly-born animals Gudden long ago showed that section of a nerve trunk gives 
rise to complete disappearance or perliaps an arrest of development of the cells of origin. 
(ii) In adult animals a somewhat similar condition has been noticed if a long time has 
elapsed since the occurrence of the lesion. 
FoREL* in 1887 cut the facial nerve in two Guinea-pigs at the stylomastoid foramen and 
allowed the animals to live 262 days and 141 days respectively ; in both cases he found marked 
diminution in the number and size of the cells in the side of the lesion. 
DARKscHEwrrscHt in 1892 also divided the facial and hypoglossal nerves, and after six 
weeks found changes in the nuclei of origin, the cells being diminished in number, atrophied, and 
shrunken. The changes found in the cord after amputations have already been alluded to and 
» Forel. 'Arch. f. Psych.' 1887. 
f Darkschevvitsch. ' Neurol. Centralb.,' p. 658. 1892. 
