Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 67 
General appearance of the Gasserian Ganglion and chief branches of the 
Fifth Nerve. 
In Embryo F. M. (see figs. 9 and 10, Plate II.), the Gasserian ganglion is egg- 
shaped, the pointed end of the egg corresponding to the upper end of the ganglion, 
just behind where the ophthalmic nerve takes origin. The long axis of the ganglion 
runs from above, downwards, and a little backwards and outwards. Its longest 
diameter is 1°3 mm., its transverse diameter 0°8 mm. The fibres of the motor root, 
which rise from the pons in front of, and to the inner side of, the sensory fibres, 
form a distinct flat band crossing the ganglion obliquely, downwards and forwards, 
on its inner side, near its lower broad end. This band of fibres is continued into the 
inferior maxillary nerve, and forms a distinct groove on the ganglion, as it crosses it, 
just as if a string had been tightly drawn across it. The cells of the ganglion 
are continued further towards the pons, on the upper and anterior part of the motor 
root than behind, and here form a deeply staining conical mass. 
The anterior surface of the ganglion possesses three little conical pro- 
jections, each of which corresponds to the origin of one of the divisions of the 
fifth nerve. These little conical elevations lie one above the other, but not directly 
so, as the first or upper is a little internal to the middle, and the middle a little 
internal to the lowest; further, the middle is behind the upper, and the lower 
behind the middle. The divisions of the fifth nerve, taking origin at these eleva- 
tions, radiate from one another in such a way that the ophthalmic and inferior 
maxillary nerves enclose between their lines of direction an angle of 90°, while 
the direction of the superior maxillary nerve bisects this angle. It is interesting 
to note that for the adult, Schwalbe* has described the courses of the first and third 
divisions of the fifth, as inclined to one another at an angle of 90°, so that probably 
the embryonic orientation of the main trunks of the fifth nerve, persists in the 
adult. 
‘The appearance of the Gasserian ganglion, and the origin of the divisions of 
the fifth nerve in Ob. and Wt. were found to correspond accurately with what 
has just been described for F. M., Ob., and Wt., being embryos a little younger, 
and a little older than I. M. 
*<« Lehrbuch der Neurologie,”’ 1881, p. 825. 
TRANS. ROY. DUB. SOC., N.S. VOL. VI-, PARI Il. L 
