1898-99.] STRUCTURE, MICRO-CHEMISTRY AND DEVELOPMENT OF NERVE CELLS. 431 
produce slight differences in distribution of all chromatin, and different 
fixing fluids also form a slightly different intergranular substance which 
would cause the granules to have a different appearance. 
Putting all things together we may conclude that during life the 
granules have the same refractive index as the remainder of the cell, but 
that they are formed elements in the cytoplasm as much as ordinary 
chromatin is a formed part of the nucleus. It is probable that all 
chromatin is more or less plastic, for different fixing fluids produce a 
slightly different disposition of chromatin in the nuclei of all cells. It 
seems to me to be impossible to answer Flemming’s objection that the 
cone of origin of the process of spinal-ganglion cells is always free of 
granules, if the latter are precipitated elements in the cell. 
Many authors, including De Quervain,™ Held, Flemming, v. Lenhossek 
and others, consider the Nissl granules are made of fine particles em- 
bedded in another substance. It is true that the Nissl granules, 
in the different cells, but more particularly in the spinal-ganglion 
cells, do not appear homogeneous. Is this due to one: kind of 
substance embedded in another different substance, or is it due 
to irregularities in contour of the same substance? 1 think the 
latter is the correct explanation. In sections tv thick and stained with 
eosin and toluidin blue, iron-alum hematoxylin or other dyes, or treated 
to liberate the “ masked” iron, the same result was always obtained ; 
the granules appeared homogeneous but of different densities. The edges 
of the granules are never straight, a circumstance that many have 
noticed, and thus a section of the cell must contain different thicknesses 
of the material. The granules often contain vacuoles, which would 
also tend to give them a heterogeneous appearance. The vacuolated 
appearance is also due to inequalities of the surface of the granules, for 
one can see in almost every preparation how a section at right angles 
to the plane being examined would appear to leave cavities in the 
chromatic material. 
I do not intend to discuss in this paper the arrangement of the Niss] 
granules in the cell, and shall refer only to the presence or absence of 
these granules in the axis cylinder and cone of origin of this process. 
The history of development would tend to show that the Nissl granules 
would not be found in the axis cylinder process, and this is what all 
observers who have worked with material that had been fixed and then 
84 De Quervain, Fritz, ‘‘ Ueber die Verainderung des Centralnervensystems bei experimenteller Kachexia 
thyreopriva der Thiere,” Virchow’s Archiv. CXXXIII, p. 527, 1893. 
