1898-99.] STRUCTURE, MICRO-CHEMISTRY AND DEVELOPMENT OF NERVE CELLS. 421 
These facts indicate that the three nuclein compounds of the adult 
nerve cell, the Nissl granules, the nucleolus and the oxyphile nuclear 
substance, are derived from the chromatin of the nucleus of the ger- 
minating cell. This chromatin divides into two parts, each containing 
iron and phosphorus, but the one is oxyphile and remains in the nucleus, 
while the other is basophile and diffuses into the cell body and becomes 
the Nissl granules. The nucleolus seems to correspond in character to 
the chromatin of such a stage as is represented in Fig. 15, where little 
change has occurred from the equatorial-plate phase. 
The cell body is filled with diffused chromatin before the protoplasmic 
processes are formed, but as the cell grows and the protoplasmic pro- 
cesses arise, the diffused chromatin is formed into masses and these in 
turn into smaller pieces until the size observed in the adult is reached. 
The breaking up of the diffused chromatin into masses is probably due 
to growth, and not to functional activity as one might think from the 
results obtained by Vas and Eve, for the ganglion cells of the retina of a 
foetal calf of 60 cm. were distinctly granular. If the process of fragmen- 
tation proceeds far enough, the masses will be isolated in the cell, but if 
not they will constitute a reticulum. No evidence was observed ofa 
connection persisting between this diffused chromatin and the nucleus. 
One criticism of the observations of His is necessary. His stage 4 in 
the development of the neuroblast should succeed his stage 5, for the 
description of the latter stage is of a cell in which the basophile 
substance has not yet diffused from the nucleus, while the description 
of the former stage is of a cell in which this diffusion has taken place. 
That such a mistake might arise is seen from the fact that the basophile 
substance is not distinct in the cell body for a long time after neuroblasts 
are formed and have migrated into the mantlelayer. Thus germinating 
cells are found in all the stages from the earliest procured (7 mm.) to 
that in which the embryos are about 18mm. long, while neuroblasts of 
the type that His describes as developed are abundant in the mantle 
layer at 7mm. and continue to be so until the formation of neuroblasts 
ceases. The chromatic substance, however, is not abundant in the cell 
body till the embryo is about 15mm. long. Consequently the process 
of transformation and diffusion of the chromatin is going on while the 
embryo grows from at least 7mm. to 15mm. In an embryo of 15mm. 
there are still many neuroblasts in the mantle layer that have not a 
distinct colourable cone but only a thickened mass of basophile sub- 
stance around the nuclear membrane. 
A single section of an embryo pig from 15 to 18mm., since it contains 
