14 J. B. JOHNSTON, 
parations. The roots stand out very distinctly, however, by reason 
of the osmic acid staining of the medullary sheaths. I believe that 
all of the fibres of these roots come from other levels by way of the 
fasciculus. If any motor cells sent their neurites directly into these 
roots, they would probably be visible in my preparations, since the 
neurites of motor cells are usually impregnated for some distance 
from the cell. 
The IX or glossopharyngeus has one ventral root which is in 
every way like the roots of the vagus just described. 
The ventral root of the VII or facialis arises chiefly from cells 
situated some distance caudal to the root, the fibres forming a distinct 
bundle in the lateral part of the fasciculus (Phot. 12). A small 
number of fibres come from cells in the immediate vicinity of the 
root. The relation of the root fibres to MAUTHNER’s cells and the 
groove of the ventral horn has been described. The further course 
of the root is like that of the IX and X roots, except that the VII 
makes its exit ventral to the spinal V tract instead of dorsal to it. 
The VI or abducens is a small nerve which arises from the 
base of the medulla at a level about mid-way between the VII and 
the N. lineae lateralis X. It has five or six very small rootlets 
placed in cephalo-caudal succession. Its fibres are heavily medullated 
and are never impregnated in my preparations. I have traced a 
few of them from the fasciculus long. post. in haematoxylin sections 
and by means of osmic acid blackening in GOLGI preparations. 
Many of them take an isolated and sinuous course within the medulla 
so that it is impossible to trace them by this means. 
The ventral root of the V or trigeminus arises by several 
bundles (seven in one case), which vary in size and arrangement in 
different individuals. The bundles leave the brain close together 
within the space of 0,8 mm. The fibres forming these bundles come 
for the most part from groups of cells situated close to the central 
cavity just lateral to the ventral horn (Phot. 14, cf. page 66). The 
caudal bundle receives a few fibres from the caudal direction 
lateral to the fasciculus long. post. which I have not been able to 
trace to their cells of origin. 
2. Dorso-lateral Portion of Medulla. 
The dorso-lateral portion of the medulla is made up of the end- 
nuclei of the sensory roots of the V, VII, VIII, IX, X, and lateral 
line nerves. These centers are divided into two groups which are 
