Hata, Mitosts in Nerve Cells. 279 
given by the authors. GrxLson’s fluid always gave satisfactory 
results. 
~ The materials preserved with the fluids mentioned, were 
carried through graded alcohols and embedded in paraffin in 
the usual way. The sections were cut three micra in thickness. 
As the staining reagents, HEkMaNn’s saffranin and gentian 
violet, Bronpi-EHRLIcH’s tri-color mixture, toluidin blue in 
aqueous saturated solution followed by erythrosin of 1% solu- 
tion in 70% alcohol, and HeipEnnHaIn’s iron-haematoxylin fol- 
lowed by either Bordeaux red or orange G in 1% solution in 
distilled water, were employed in each case. 
In general, HEIDENHAIN’s iron-haematoxylin followed by 
Bordeaux red or orange G gives a very satisfactory staining of 
the mitotic figures. However, for the structure of the chrom- 
atic thread, for the relations of linin to the chromatin, and 
especially for the peculiarities of the nucleolus in active divis- 
ion, as well as during the resting stage, HERMANN’s or BIONDI- 
EHRLICH’s staining method gave more satisfactory results. The 
writer used also Nissi’s methylen-blue method, but the results 
were less satisfactory than those obtained from the fluids just 
mentioned. In each case, the sections should be stained slowly 
by long immersion in dilute solutions; otherwise, artifacts are 
obtained. 
III. Germinal cells, or ‘‘Keimzellen.”’ 
In an early stage of development, the central nervous sys- 
tem is formed by a long continuous tube composed of several 
layers of the epithelial cells derived from the ectoderm. The wall 
of the neural tube soon becomes thicker as a result of the pro- 
liferation of the ectodermal cells of the primitive tube. This 
prolifieration is due to the division of the cells which lie near 
the lumen of the tube. These cells were called germinal cells 
or ‘‘Keimzellen” by His.' 
Whether at some time in their history all the ecto- 
dermal cells which form the primitive neural tube. un- 
1 His: Die Neuroblasten und ihre Entstehung im. embryonalen Mark. 
Abhandl. d. Nat. Phys. Kl. d. Konigl. Séchs. Gesellsch. d. Wiss. Bd. 15, ’89. 
