Hatal, Centrosome in Nerve Cells. 27 
marked sphere. In the adult white rats, however, the nerve cells 
which contain these structures are by no means so abundant. 
The following table shows the localities in which the cen- 
trosome was observed : 
TABLE I. Showing the groups of the cells of the white rat in which cen- 
trosome has been found. 
Largest cells Nucleus _ of|Motor cells in 
in cerebral|Purkinje’s _ |corpus denta-|ventral horn/Cells in spi- 
Age cortex cells tum spinal cord |nal ganglion 
Adult present present fo) fo) present 
“Young | present | | present | | present | — present | present 
It is interesting to find that the centrosome is so widely 
distributed through the central nervous system, of the young 
as well as the adult white rat, while some authors—viz., NELIS, 
FLemminc—claim that the centrosome can not be found in the 
normal nerve cells of the higher mammalia. In adult animals, 
the writer could not find the centrosome either in the nucleus 
of the corpus dentatum or in the cells in the ventral horn of 
spinal cord, although it was clearly to be demonstrated in these 
localities in the case of young animals. It is a reasonable sup- 
position, however, that the invisibility of the centrosome in 
these two regions in the adult white rat is due to the large quan- 
tities of the stainable substance which fills up these nerve cells 
and thus obscures the presence of the centrosome. The writer 
noticed, very often, structures similar to the centrosome in both 
these regions; but was unable to determine its structure with 
certainty because not only the clear space but also the radial . 
arrangements of cytoplasm, which is most characteristic for the 
centrosome, were obscured by the presence of many small 
granules of a uniform size. 
The writer believes, however, that moreimproved methods - 
both in preserving as well as staining would overcome these 
difficulties and reveal the centrosome in these localities also. 
