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steps of division under certain forms of stimulation, as has been 

 observed bj some investigators; but in the normal state the centro- 

 some in an adult cell presents slight morphulogical differences from 

 that of the embryonic cell, which we interpret as the beginning of 

 degeneration". Hatai comes finally to the conclusion that the only 

 way to find out whether there is generally a division of ganglion 

 cells in the spinal ganglion is to count the number of ganglion cells 

 in corres{)onding ganglia in animals of different ages. Hatai counted 

 the ganglion cells in 6' VII, ThW and L\\ in four specimens of 

 Mus norwegicus albimis weighing 10,3, 24,5, 68,5 and 167 grammes 

 respectively. I have given a synopsis of the results of his calculations 

 in Table b above. At the outset I wish to make this criticism 

 on his calculations, namely, that he has contented himself with 

 counting the number of ganglion cells in only one spinal nerve in 

 each of the cervical, thoracal and lumbal regions. Great variation 

 may exist in these, as I have had abundant opportunities of observing 

 during my counting of axons. These variations may be so great that, 

 in a species in which the total increase of the number of nerve fibres 

 in the dorsal roots during post-embryonal growth is, let us say, 

 100 per cent., certain nerves in the few days' old individual 

 may, in spite of this, contain more nerve fibres than the corresponding 

 nerves in the full-grown animal.^) My continued investigations have 

 also shown that a similar variation may be found in the number 

 of ganglion cells in the spinal ganglion. In this case one has to 

 investigate a rather large number of spinal ganglia in order to 

 obtain reliable information by the method used by Hatai. On account 

 of the values obtained by counting (Table b) H. concludes that "the 

 total number of the spinal ganglion cells remains approximately 

 constant between 10,3 and 167 grams, though individual variations 

 in the numbers of the cells in corresponding ganglia exist. It can 

 therefore be stated that this number does not increase or decrease 

 with age." We must, however, note that the number of ganglion 

 cells was throughout larger in the older specimens (Table i^), although 

 the excess in the numbers was not so great. Hatai puts these larger 

 numbers of cells in the older individual within the limits of the 

 variations. It seems as if he cannot admit the possibility that a 

 division of cells in a spinal ganglion might occur. Hatai reveals this 

 especially in his criticism of Bühlek's') observations. Bühler writes: 

 "Es kommt wie ich mich bei Frosch und Kröte und auch beim 



1) Further details about this will be given in the more complete account. 

 ^) Bühler, A. Untersuchungen fiber den Bau der Nervenzellen. Verb. d. Phys. 

 raed. Ges Würzburg. N. T. Bd- 39, 1898 Git. nach Hatai (1902). 



