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structures appear, but where tlie protoplasm has a marble appearance. 

 Tlie cells with the evident neurofibril structure may be of the most 

 varying sizes and iimy also occur in different stages of development; 

 this is shown, among other ways, by the fact that in mammals of 

 post-foetal ages a few bi-polar cells are found in this group, besides 

 the ordinary unipolar cells, (see fig. 12). The cells that are without 

 any neurofibril structure, or have merely traces of this, are similarly 

 of very different sizes, and on several of them I have found 

 formations which could hardly be interpreted otherwise than by 

 assuming that the cell is dividing amitolically. On the other hand 

 I have not in a single case been able to observe any indications of 

 amitotic division in a cell of the former type, in which the neuro- 

 fibi'il structure was evident. The apolar cells also belong to this 

 category . 



In a number of preparations from the spinal ganglia of young 

 animals (dogs) I have found colonies of nerve-cells situated within 

 the same capsule. The number of cells in these colonies varied con- 

 siderably. Fig. 4 shows one of these colonies with seven cells, in 

 which at a few places pi'Otoplasmic bridges (bridging fibrils) go 

 from one cell to the other; there are no processes, and the cells 

 show a pale shade of colour; there is no neuro-fibril impregnation. 

 The references in liteiature to this condition and a more detailed 

 description of it will be given below. Traces of this difference in 

 neuro-fibril impregnation which is found in the spinal ganglia are 

 also seen in the central nerve system, although it is not so striking there. 



These facts have led me to set up the following working hypo- 

 thesis: The affinity of the neuro-fibrils in the nerve-cells to the 

 silver salts (reducing power) seems to vary from being more or less 

 powerful to total disappearance during certain metabolic or functional 

 stages. The majority of the pale cells seem thus to belong to such 

 an early stage of development that no neuro-fibrils have yet been 

 fully developed in them. 



We ha\e now reached the heart of the problem of division, viz. 

 the increase of the ganglion cells in the spinal ganglion. With regard 

 to this problem Hatai ^j writes as follows: "We can only say at 

 present concerning the division probletn that the nerve cells in 

 vertebrates, as well as in invertebrates, have the centrosome and 

 the sphare, which are regai-ded as the dynamic centies of the mitotic 

 divisions, and, further, that this centi'osome is able to take the first 



Hatai, S. On the Presence of the Centrosome in Certain Nerve Cells of the 

 White Rat J. Coinp. Neur. Vol. XI. N«. 1. 1901. 



