CRANIAL NERVES OF SILURUS AND MORMYRUS (i 
micrometer. If the most ventral part of the bulb was not in the 
region of the raphé, it was projected on the sagittal plane of the 
raphé. The micrometer being put parallel with the raphé, a 
movement of the object table perpendicularly to the micrometer 
was sufficient to project the point in question on the medial plane. 
At the dorsal limit of the bulb the first curve toward the hori- 
zontal in the lining of the ventricle was registered. In the same 
way the ventral and dorsal limits of each nucleus were registered 
and projected on the medial plane. 
In my projections each section was counted as 2 mm. Since 
each section was 25 micra thick and the series contained only 
alternating sections, these 2 mm. represent 50 micra, thus giving 
an enlargement of 40 diameters. The same magnification was 
applied to the dorso-ventral dimensions, which likewise gave the 
natural relations forty times enlarged. 
Since my projections have been four times reduced for repro- 
duction, the figures represent the natural relations ten times 
magnified and projected on the sagittal plane through the raphé. 
The ventral border of the medulla has been taken as a horizontal 
line. It is actually slightly curved, but the curve of the oblongata 
in teleosts is generally so insignificant that the error hereby 
introduced has only a slight influence on the exact relations. 
Figure 2 shows the projected points connected by lines. The 
dotted line represents the floor of the ventricle, or rather, since 
the ventral border of the bulb is drawn straight, it represents 
the algebraic addition of the curves occurring in the floor of the 
ventricle and those in the ventral border of the bulb. 
The limits of the nuclei are indicated by full lines, in doubtful 
cases by dashes alternating with dots. Local interruptions 
in the nuclei are indicated by curved lines. Beneath the base 
line, representing the ventral border of the bulb reduced to a 
horizontal line, the levels of entrance of the motor roots are 
registered, thus enabling us to see the distances between the roots 
and the spaces occcupied by their entrance. 
Figure 3 is based on figure 2 and is designed to give a simpler 
view of the relations, the curves being smoothed by the omission 
