214 The Anatomy of a 12-mm. Pig 
The spinal accessory nerve begins at the level of the sixth cervical 
ganglion. Its fibres are very closely associated with the hypoglossal 
ganglia; in series 518 it rests against, and in places is nearly sur- 
rounded by the first cervical ganglion. The passage of fibres between 
the latter and the spinal accessory nerve has been found in man by 
Kassander, and corfirmed by Froriep and Beck, 95 (p. 694). 
Of the sense organs, only the nasal cavity need be noted. Plate-2 
is drawn to show the relations of the pharynx and some other internal 
structures to the surface markings. The nasal cavity appears with 
the external naris opening broadly on the surface. Toward the mouth 
the two edges of this cavity are brought together by the growth of the 
median nasal process on the inside, and of the lateral nasal and maxil- 
lary processes (separated by the lachrymal groove) on the outside. 
Caught between the internal nasal and maxillary processes, the walls 
of the nasal opening are compressed to form a raphe of semicircular 
outline as shown in the figure. This raphe extends to the roof of the 
oral cavity. At its internal end it is a mere plate, indicating the posi- 
tion of the internal naris. In the 14-mm. pig the raphe has disinte- 
erated and mesenchyma extends from side to side. The membrane is 
at is internal end, after becoming broad and thin, ruptures. Hochstet- 
ter, 92, states that “the primary choane of mammals arise from a 
breaking through of the hind end of the nasal pit by a tearing apart 
of the membrana bucconasalis, and there exists in mammals no primary 
connection between the nasal and buccal cavities.” Peter, 02, pp. 54- 
5), adopts this interpretation. The new opening, however, appears to 
involve only a part of the raphe made by the fused lips of the primitive 
nasal opening. The fusion is permanent except in the region of the 
from the entodermal tract. 
Pharynz, Digestive Tract, and Viscera.—The structures connected 
with the roof of the mouth are shown in Plate II, and in median section 
also in Plate III. Beginning anteriorly there first appears the hypo- 
physis, having a slender outlet and a broad, thin, spade-like body, flat- 
tened parallel with the brain wall. It tends to fork at the infundibular 
gland and possesses an inconstant knob near the junction of its body 
and duct. Behind the duct there is still to be seen Seessel’s pocket; 
between it and the hypophysis the oral membrane formerly separated 
the stomadzum from the entodermal tract. 
The floor of the oral cavity is shown in relief in Plate III. Most 
anteriorly are the large mandibular arches. From the broad dorsum 
of each arises an elongated eminence, rounded in cross section. In the 
median line between them, there is a groove in the caudad part of 
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