MAUTHNER’S CELL 111 
ular and elongate, as may be seen in figures 6, 11 and 12. Fig- 
ures 7, 8 and 9 show that the Nissl bodies of the Mauthner’s cells, 
the Miiller’s cells and the other large cells of the nucleus motorius 
tegmenti are practically identical in size and shape, though they 
are not so abundant in the last mentioned type. They are, in 
fact, quite distinctive of the cells of this nucleus. 
Neurofibrillae. All kinds of preparations show neurofibrils in 
Mauthner’s cell, provided only the sections are cut thin enough. 
Mayser saw them clearly in his carmine preparations. This is, 
in fact, an ideal material for studying the chromidial substance 
and fibrillae side-by-side under different physiological conditions 
of fatigue, etc. It is interesting to note that in many Cajal prep- 
arations the fibrillae appear thicker in Mauthner’s cell than in 
any others, but this difference cannot be perceived in the more 
reliable formol-osmic-Zenker material. 
The mitochondria and other cytoplasmic granulations have 
not been studied carefully because they are not sufficiently well 
preserved in my material to make the identification certain. 
The great medullary sheaths on the periphery of the oblongata 
reduce the osmic acid rapidly so that it does not penetrate in 
time to fix these structures. In Mauthner’s fiber the mitochon- 
dria are short rods arranged parallel to the neurofibrillae. Simi- 
lar structures are shown in figure 13 within the lateral dendrite, 
but they cannot be definitely identified as mitochondria. The 
granules shown in figure 12 doubtless correspond to Held’s neuro- 
somes, but as Cowdry (’12) has shown this term includes two 
distinct categories of cytoplasmic granulations which are not dis- 
tinguishable after sublimate fixation. 
DISCUSSION 
The nucleus motorius tegmenti bulbi is primitively a codrdi- 
nating mechanism for the motor apparatus of the bulb and cord. 
Edinger has emphasized the importance of this point and it is 
substantiated by the position of the nucleus in the somatic motor 
column, by its relation to the fasciculus longitudinalis medialis, 
by the internal structure of the cells and their grouping in the 
region of the bulbar motor nuclei. The last point has not been 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 25, NO. 1 
