1898-99.] STRUCTURE, MICRO-CHEMISTRY AND DEVELOPMENT OF NERVE CELLS. 429 
1V.—SOME GENERAL CONSIDERATIONS ON THE STRUCTURE OF 
THE NERVE CELLS. 
It may seem strange to revert to this subject, but owing to the fact 
that the Nissl granules were thought to be cytoplasmic structures, sever- 
al views concerning the structure of nerve cells have been advanced 
that would not have been if the true nature of the granules had been 
known. 
The first question is, whether the Nissl granules are formed elements 
of the cell body, or are precipitated while the cell is dying or when 
it is affected by the fixing agent. Held® accepts the latter ex- 
planation, as he claims to have seen fresh cells in which there were 
no granules but a homogeneous cell body. On standing for a few min- 
utes the cells become granular, thus showing the granules were precipi- 
tated while the cells were dying. On adding water to the cells they 
become vacuolated, but the vacuoles would ‘collapse on adding a fixing 
agent, thus leaving the granules around a vacuole. Held also believes 
that the granules are soluble in alkalies, and that the normal reaction of 
the nervous system is alkaline, but it becomes acid shortly after death, 
and that this is the reason the cells contain vacuoles in tissue hardened 
in alkaline alcohol. 
v. Lenhossek and Flemming say the granules are visible in the fresh 
condition shortly after death. Each animal has a typical form of gran- 
ule in the spinal ganglion cell, whatever fixing fluid has been used, 
which could not be if the granules were precipitated either in dying 
or with the acid reagent. 
Buhler maintains that the granules are not seen in a fresh state, or 
even in a fixed condition, but this is no argument for their non-existence 
in the living cell, for the nucleus is often invisible in a fresh state. 
Ruzicka believes the granules are only due to differentiation in stain- 
ing, because if you overstain you do not see them, and if you extract too 
much they are invisible. 
I agree with Held and Bihler that these granules are invisible in a 
fresh condition, and with Biihler also that the granules are hardly visible 
as such in the fixed cell. Ifone examines an unstained section ofa spinal 
82 L.c., 1895. 
