129 
indicated by a spot in the chart, the second branch arises. 
This is the R. bucealis. It at once splits into a dorsal and 
a ventral division. The former itself divides as it passes 
through the skull wall above the trigemino-facial foramen 
into a posterior R. oticus and an anterior R. buccalis 
externus. The latter is the R. buccalis internus, and 
leaves the cranial cavity by the trigemino-facial foramen. 
2. R. oticus (7. of.)—Passes almost straight upwards 
and splits into two, one passing straight forwards and the 
other, except for the curious bend at its termination, 
straight backwards. The former supplies sense organ 13 
of the infraorbital canal, the latter, after being reinforced 
as above described, sense organs 14 and 15 (the last two). 
3. R. buccalis externus (owt. buc.)—Passes down- 
wards and forwards, gives off a twig to sense organ 12 of 
the infraorbital canal, and then courses as shown in the 
chart to supply sense organs 7 to 11 of the same canal. 
The first 7 sense organs of this canal were not enclosed at 
the stage at which the sections were cut, and were hence 
lying freely on the surface. The first three are supplied 
by the R. buccalis internus, but no nerves could be traced 
to the fourth, fifth and sixth sense organs. This is due to 
the fact that the outer buccal nerve, after supplying sense 
organ 7, becomes extremely thin, and as it coursed among 
the numerous pigment cells on this, the ocular, side, could 
not be traced. It is most probable, however, that it sup- 
plied sense organs 4, 5 and 6. Comparison with the 
eyeless side, where there is no pigment, does not help, as 
the canal is shorter and develops more quickly. 
4. R. buccalis internus (77. bwc.)—Leaves the skull 
cavity by the trigemino-facial foramen and accompanies 
the superior maxillary nerve. In front, opposite the 
infraorbital canal it divides into an upper inner buccal 
(up. in. buc.) and a lower inner buccal (low. zn. buc.). The 
M 
