1025 



this figure as a spinal gaM^Iion cell at sncli an early stage of deve- 

 lopment that it had not lost its power of increasing in number 

 through mitotical division. I found another mitosis of this kind in 

 the sei'ies just mentioned. Among the other group of mitoses, 

 namely those in cells that are situated inside or in the capsule of 

 an older ganglion cell, my preparation shows at least a few forms 

 in which one can clearly follow the capsule peripherally of the cell 

 that is engaged in mitotic division and where the latter must therefore 

 be situated beneath the capsule. Thei-e are thus good reasons to 

 support the assumption that, even among this group of mitoses, 

 some are to be referred to very young undifferentiated cells, which 

 on good grounds — for instance on account of their position — 

 can be assumed to develop into nerve cells. By far the larger 

 number of mitoses are, however, undoubtedly to be referred to 

 ordinary capsular cells. But is the difference between the capsular 

 cells and the nerve-cells really so great? Are not the former perhaps 

 to be regarded as matiix cells for the latter? 1 must leave these 

 problems to a subsequent and more detailed account of this question 

 and confine myself to saying that there ai-e points in the prepa- 

 ration that support such an assumption ^). These facts are all the more 

 worthy of attention because, among the investigators who formerly 

 looked for mitoses in spinal ganglia, Flemming '), Daal and Len- 

 HOSSEK have been unable to show any in young animals. Müi>ler '), 

 on the other hand, found them in new-born animals, but in no 

 later age. The very largo number of mitoses in the sj)inal ganglia 

 shown in the present and other investigations of young animals 

 clearly support the considerable post-embi-yonic increase in the 

 number of capsular cells in this region, an increase that could 

 scarcely be explained if the ganglia ^ did not increase in number 

 too. In my opinion the exceedingly great num[)er of mitoses that 

 are found in the spinal nerve-cells, accoi'ding to what has been 

 shown above, cannot possibly be explained by an increase in size 

 merely of those spinal nerve-cells which were already present at 

 biith. This is the less probable because the spinal ganglion-cells 

 must decrease in number with the years, if new ones do not grow 

 out and replace all those that degeuei-ate and die away during 

 postTembryonic life. And this degeneration of the nerve-cells is 

 admitted and shown by all the chief investigators of this problem. 



1) See addendum! 



2) Flkmming, Daal and Lrnhosskk. Quoted from Müllkr E. 



^) Muller Erik, Untersuchungen iiber den Bau der Spinalgangiien. Nord. med. 

 Ark. Stockholm. Bd. '23. 1891. 



