No. 1.] AMPHIBIAN BRAIN STUDIES. 65 
lateral columns of the cord; at least, no special group of nerve 
cells has been observed contributing to it. The fasciculus 
communis, however, is closely applied to a nucleus of small 
sensory cells, fcz., from which it appears to be reinforced. The 
fasciculus solitarius enters the two posterior roots. (3) 
The three middle roots arise from the nucleus in the floor of 
the ventricle, 10 x, which is apparently composed of sotor 
cells. (2) The two anterior roots, a, 4, arise from the fasci- 
culus communis, which is thereby reduced to a small bundle. 
The Glossopharyngeus arises from four sources. 1. The fas- 
ciculus communis. 2. A large sensory nucleus. 3. A 
nucleus of doubtful motor cells. 4. A motor nucleus in the 
floor of the 4th ventricle. (2) The sensory nucleus and tract 
is found at a low level opposite the exit of the posterior roots 
of the 1oth. This tract 9 ¢ rapidly increases in size from the 
nucleus in the dorsal folds of the medulla, which is undoubtedly 
sensory. Anteriorly, this nucleus is replaced by the sensory 
nucleus of the 7th, and below it, in the angle of the medulla, 
(3) is a small nucleus of cells of different character which are 
probably motor, 9 mz. These doubtful cells have the same 
position as the nucleus of the lower root of the 7th pair, 
which is unquestionably motor. The fibres from these two 
nuclei constitute a single tract, and form the anterior root of 
the oth nerve. (4) The motor nucleus in the floor of the 
ventricle, gz, is in exactly the same position as that of the 
1oth pair, and is composed of spindle-shaped, probably motor, 
cells. The fibres from this nucleus form the posterior root. 
(1) The fasciculus communis forms the middle root. 
The oth and roth pairs have in common, first, the continuous 
and closely similar sensory nuclei and tracts arising from them 
which constitute the main sensory supply of the former nerve; 
second, the special motor nuclei in the floor of the ventricle; 
third, the fibres of the fasciculus communis, also sensory. 
The element of doubtful motor cells which is present in the 
oth and absent in the roth, may subsequently be found in the 
latter. The goth, however, apparently lacks the fasciculus 
solitarius. The special motor nuclei, 9 z and 10 %, are seen to 
correspond in position to the lateral portions of the anterior horn, 
z.e. to the region dorsal to the extremity of the anterior horn. 
The Acusticus. The nuclei and tracts of the 8th pair, 
