EEE ee 
ee eS 
THE DEEP CONNEXIONS OF THE CRANIAL NERVES. 479 
round bundle of longitudinal fibres which forms a very conspicuous object in trans- 
verse sections through the medulla. It begins at the upper limit of the medulla, 
and can be traced downwards through its whole length. Its precise point of 
termination is not known, but it is believed that it 1s carried for some distance 
downwards into the upper part of the cord, viz. to the level of the fourth cervical 
nerve, according to Kolliker. The relations of the fasciculus solitarius are not 
the same in all parts of its course. It lies immediately to the outer side of the 
vago-glosso-pharyngeal nucleus; but whereas in the upper part of the medulla 
it is situated somewhat on the ventral side of that nucleus, in the lower 
closed part of the medulla 
it is placed on its dorsal 
aspect. Throughout its 
entire length it iS inti- 
mately associated with a 
columnof gelatinous gray 
substance which consti- 
tutes the nucleus of ter- 
mination, in which its 
fibresend. When traced 
from above downwards, 
the solitary tract 1s ob- 
served to become gradu- 
ally smaller from the 
loss of fibres which it Se 
. r A 
thus sustains. The great Fe SK 
bulk of the solitary tract EOCHLEAR N.—XTU0 ACCUM 
is formed of fibresderived 
MIDDLE 
PEDUNCLE 
OF 
CEREBELLUM | 
levels come to an end in 
the associated gelatinous 
gray nucleus. 
=x ele 
from the glosso-pharyn- = “°S°""* zee 
geal nerve; only a few of WNaus orale 
the afferent fibres of the Se 
vagus enter it. As the =\*|¢ 
fibres of the two nerves Ze 
join the tract they im- z| ae 
mediately turn down- alvecie 
wards, and at different ol =ele 
a r) 
; 
As the root-bundles of 
the vagus and the elosso- Fra, 356.—DraGram, showing the brain connexions of the vagus, glosso- 
pharyngeal nerves traverse pharyngeal, auditory, facial, abducent, and trigeminal nerves (founded 
the substance of the on a somewhat similar diagram by Obersteiner). 
medulla in a backward and inward direction to reach the fasciculus solitarius and the 
nucleus of termination, they pass through the spinal root of the trigeminal nerve and the 
substantia gelatinosa Rolandi associated with it. The term ascending root is sometimes 
applied to the fasciculus solitarius; but as this conveys an altogether false conception 
of its character, it should be discarded. The axons of the nucleus of termination and 
of the nucleus of the fasciculus solitarius form central connexions with other parts of 
the brain, but these have not as yet been completely elucidated. 
The nucleus ambiguus (Figs. 341, p. 458, and 343, p. 460) is the nucleus of 
origin of the motor or efferent fibres which join the vagus and glosso-pharyngeal 
nerves. The cells which compose it are large, multipolar, and similar in every 
respect to the large cells in the ventral horn of gray matter of the spinal cord. 
These cells are arranged in a slender column which is best developed in the 
upper open part of the medulla. Here the nucleus can easily be detected in 
transverse sections as a small area of compact gray matter which les in the 
formatio reticularis grisea, midway between the dorsal accessory olive and the sub- 
stantia gelatinosa Rolandi. It therefore lies more deeply in the substance of the 
