Or 
Charles R. Essick 12 
and ends at the attachment of the tela choroidea is particularly well 
shown. It compares with the right half of my figure 1 except that the 
free edge is apparently lacking, possibly having been torn away with the 
pia. Plate XXXVIII, Figs. 5 and 6, also give admirable pictures of this 
region; attention might be called to the free edges of the ponto-bulbar 
body on both sides of the former figure. 
HIstoLocicaL APPEARANCE. 
On microscopical examination it is found that the ponto-bulbar body 
consists of a mass of multipolar ganglion cells supported in a dense neu- 
roglia network closely resembling the nuclear masses of the pons. The 
Jateral or free surface of this ganglionic body is entirely covered by a 
layer of medullated nerve fibers which in general follow the direction 
of the long axis of this structure and continually give off collaterals 
which branch among the underlying ganglion cells. On its median sur- 
face throughout its greater extent there is no such layer of fibers present 
and consequently the ganglion mass lies directly adherent to the adjacent 
structures and fuses more or less completely with them. The ponto-bulbar 
body presents a uniformity of histological structure throughout, so that 
in passing from section to section the same characteristics can be made 
out everywhere. ‘he cells lie very close to one another and in large areas 
are separated from each other by less than the width of a cell. The 
narrow space between the cells is found to be filled by a dense frame- 
work of neuroglia and an intricately interwoven network of very fine 
nerve fibers, which in their complexity and number resemble the hypo- 
glossal nucleus. On the other hand this rich felt-work stands out in 
contrast to the ala cinerea, which in Weigert sections gives such a clear 
picture. 
The cells are of the multipolar type and show several different forms ; 
many are spindle-shaped with their long axes parallel to the fibers; while 
most have the characteristic multipolar form. The former are found in 
greater numbers in the part of the ponto-bulbar body’ which lies lateral 
to the restiform body, the latter in the rest of the body. The size is fairly 
uniform, so that, of cells which were measured in sections stained in 
thionin, the average was 23 x 14.5 p, some cells being as large as 29 x 17 p, 
others only 17x10 w. This corresponds exactly to measurements taken 
of the ganglion cells scattered through the pons. To afford a means of 
comparison, cells from the hypoglossal nucleus were measured in the 
same sections and were found to be 40x23 p. These measurements 
