965 



Kaninchen überzeiigen kpnnte, [)liysiologischer Weise zum üntergang 

 speziell der grossen Spinalganglienzellen. Die Degeneration verlauft 

 in verscliiedenen Formen nnd allem Anschein nach wenig rapid.;. 

 Man siet in einein Spinalganglion des Frosches ca. 20 — 25 unter- 

 geliende Zeilen, beini Kaninchen relativ nocli viel weniger. Die ver- 

 loren gegangenen Zeilen miissen ersetzt werden nnd dies gescliielit 

 vvahrscheinlich dadnrcli, das eine der kleinen durch Wachstuni ihre 

 Stelle einnimint. Da nacii deni früliesten Jngendstadinm eine Vermelirung 

 vou Nervenzellen nicht mehr vorkommt, innss das Spinalganglion, 

 um tur die Zeit des Lebens funktionsfahig bleiben zn können, in 

 der Alliage genügendes Ersatzniaterial in Gestalt von Reservenzellen 

 mitbekominen. Genanere üntersuchnngen hierüber zn rnachen, bin 

 ich indessen noch nicht in der Lage gewesen." With regard to this 

 Hatai states: "The above interpretation given by Bühler concerning 

 the small cells cannot be accepted as far as white rats are concerned, 

 for he regarded the small cells as replacing the degenerated large 

 nerve cells; if this were the case, then the total number of the 

 spinal ganglion cells must be decreased, but the preceding table 

 shows that the total number is approximately constant." 



I have observed in a number of cases in preparations fi'om dogs 

 that a number of the larger nei've-cells in the spinal ganglion show 

 signs of being in process of degeneration, and in my opinion BOhleh 

 is right in saying that these degenerating cells are replaced by 

 young cells which grow out in their place. Hatai's argument to the 

 contrary: "If this were the case, then the total number of the spinal 

 ganglion cells must decrease" proves nothing at all. It is even fairly 

 certain that the degenerate cells aie replaced by young cells, which 

 grow out and, notwithstanding this degeneration, increase the ab.solute 

 number of ganglion cells during the post-embryonal growth. As a 

 matter of fact, Hatai has unconsciously proved this last point by 

 his calculations (Table h), and his evidence in favour of it would 

 certainly have been very much clearer if he had made use of greater 

 material and had counted the cells in a larger number of corre- 

 sponding spinal ganglia in the animal investigated. 



The calculations I am making (which I have, however, not yet 

 completed) of the number of ganglion cells in the spinal ganglia of 

 animals of different ages in the same litter, seem to show that there 

 really is an increase in the number of ganglion cells during post- 

 embryonal life, although this increase is not nearly so large as the 

 increase in the axons. My preparations have also afforded information 

 as to the way in which this increase is brought about. 



{To be continued)- 



