72 OSBORN. [Vot. II. 
of the motor portion of the 7th, as found in the higher verte- 
brates, takes its exit with the 5th in the Uvodela, while some of 
the sensory portion of the 5th takes its exit with the 7th, proba- 
bly as the upper or sensory bundle which immediately joins the 
5th. 
The roots of the Glossopharyngeus seem to be in a simi- 
lar manner complementary to those of the Vagus, since the 
former nerve receives a large bundle from the dorsal sensory 
nucleus, as well as from the lateral motor nucleus, neither of 
which bundles, so far as I have observed, enter into the 1oth. 
Group B. The exit of the Abducens from the central re- 
gion of the medulla, and the special connection of its nucleus and 
those of the other eyeball muscles with the posterior longitudi- 
nal fasciculus, seems to separate these three nerves sharply from 
the Vagus or Trigeminus system, and unite them closely into 
a group of their own. Iam well aware that some grounds are 
found in the development and peripheral distribution of these 
nerves for considering the 4th or 6th as vagrant portions of the 
Trigeminal or Facial motor roots, but the internal origin cer- 
tainly does not support this hypothesis; at the same time it 
cannot be said to disprove it. 
Group C. The Auditory has been shown to differ widely 
from the oth, 5th and 7th nerves by deriving no fibres from the 
dorsal sensory nucleus, although a purely sensory nerve. This 
can be stated with considerable certainty. One of its special 
nuclei is also composed of cells of a unique character, viz., 
pale ganglion cells. The reception of fibres from the ascending 
tract adjoining the posterior longitudinal fasciculus further 
distinguishes it from the nerves of group A.} 
These considerations lead to the following provisional con- 
clusions in regard to the zztra-axial origin of the cranial nerves 
in the Amphibia. 
1°, That there is a close similarity Detween thie 
disposition of the nuclei and tracts of the IX.— 
X. and V.-VII. groups, the nerves of these groups 
being complementary to each other, and together 
apparently containing fibres from two sensory nu- 
clei and from two motor nuclei. The extreme dor- 
1 See Appendix, Note 3. 
