1898-99. | STRUCTURE, MICRO-CHEMISTRY AND DEVELOPMENT OF NERVE CELLS. 419 
and an inner granular layer. The next distinct stage which His dis- 
tinguishes in the development of the nerve cell is the neuroblast phase. 
Here an oval nucleus bears a conical cell body, and this in turn is con- 
tinued into a long process. The nucleus is moderately rich in chromatin 
of which there are several masses united by a filament. There are no 
protoplasmic processes and the protoplasm around the nucleus is very 
scanty. The neuroblasts arise in the inner layer from the germinating 
cells and pass out secondarily into the mantle layer of the wall. In the 
transformation of the germinating cells into neuroblasts His distinguishes 
five stages : 
(1). Germinating cells of round form with a broad protoplasmic body. 
(2). Germinating cells of round form with initial point and broad pro- 
toplasmic mantle. 
(3). Intermediate cells of pear shape with little protoplasm around the 
unclosed nucleus. The cytoplasm is continued into a long process and 
the cells may still lie close to the internal membrane. 
(4). Intermediate cells of pear shape with closed nucleus, deeply 
staining, outer cone, but little protoplasm around the remainder of the 
nucleus. 
(5). Finished neuroblast. 
My observations confirm those of His on the origin of the neuroblasts 
and in addition show the fate of their chromatin, a point not touched 
upon by His. 
Germinating cells occur in the pig from the earliest stage procured by 
me (7mm.) to that of 18mm. length. If a section of a cord of, 22, a 
1omm. pig, is stained with eosin and toluidin blue, one finds that all 
the blue-staining substance in the germinating cells is confined 
to the chromatin of their nuclei. The reactions for iron demonstrate 
that the cytoplasm is devoid of substance containing this element. At 
this period all iron-holding material is confined to the chromatin of the 
nucleus. 
These cells are of round or oval shape, (Fig. 12),and are in some stage 
of mitosis. The cytoplasm is free from iron-holding material, or from 
material staining with toluidin blue. The cells are sometimes in the 
loose-skein phase, sometimes in the dyaster stage but most frequently 
in the equatorial-plate phase. The cells are generally in the equatorial 
plate phase when the process begins to be formed. As the cone in- 
creases the chromatin becomes excentric (Figs. 13 and 14). There is 
