76 C. J. HERRICK AND G. E. COGHILL 
THE MEDULLA OBLONGATA OF LARVAL AMBLYSTOMA™ 
The medulla oblongata and cranial nerve roots of half grown 
larvae of Amblystoma have recently been analyzed (Herrick, 
14), and some very interesting relations have come to light. 
The functional components of the roots and peripheral branches 
of the cranial nerves of old larvae and adults of Amblystoma 
tigrinum, have been previously analyzed by Coghill (01, ’02) 
and the more recent observations of Herrick show that in younger 
larvae essentially the same functional pattern is present in the 
nerve roots as in the older specimens described by Coghill. It 
is necessary therefore here merely to call attention to the fact 
that the components of the cranial nerve roots in the half grown 
larvae here under consideration conform in all respects to the 
arrangement which is characteristic of the adult forms of the 
Ichthyopsida in general, as elucidated in a large number of Pe 
by recent students of nerve components. 
This implies that each physiological type of peripheral ie 
organs has its own distinct ganglia and nerve roots in the medulla 
oblongata. The nerves of general sensibility enter the brain 
through the V, X and probably the VII roots and pass into the 
spinal V root. The nerves of general visceral sensibility and 
taste enter by the VII, IX and X roots and pass into the fas- 
ciculus solitarius. The fibers from the internal ear (VIII root) 
enter a longitudinal tract lying immediately dorsally of the 
spinal V tract; those of the lateral line X roots enter two similar 
tracts lying farther dorsally; and those of the lateral line VII 
roots enter three such tracts, one between the two lateralis X 
roots and two above the dorsal lateralis X root. 
Each root fiber of all of these components, without exception, 
immediately upon entering the medulla oblongata divides into 
ascending and descending branches which pass respectively 
upward and downward for long distances, thus forming the tracts 
of root fibers to which reference has just been made. These 
root bundles extend through practically the entire length of the 
medulla oblongata, maintaining throughout the same relations to 
each other, so that cross sections through all parts of the medulla 
