THE DIGESTIVE SYSTEM. wir 
distributes visceral motor branches to certain muscles (masticatory 
group, mylohyoid and digastric) regarded as belonging to this, the 
first arch. A visceral sensory connection with the mouth is con- 
sidered to be formed by the lingual branch of the mandibular nerve 
and by the palatine branches of the spheno-palatine ganglion. 
Both are, however, connected with the central nervous system 
through the seventh nerve, the former by the chorda tympani, 
and the latter by the great superficial petrosal. 
The seventh, or facial nerve, is the nerve of the second, or 
hyoid arch. It is chiefly distributed as a visceral motor nerve to the 
cutaneous muscles of the head, but contains also taste fibres from 
the tongue. The ninth, or glossopharyngeal nerve, belonging 
to the third arch, the tenth, or vagus, belonging to the fourth and 
succeeding arches in lower forms, and the eleventh, or spinal 
accessory nerves, the latter apparently related to the vagus as a 
motor portion, are distributed as visceral motor nerves to the 
pharyngeal and laryngeal musculature, and as visceral sensory 
nerves to various visceral organs, the ninth nerve supplying the 
gustatory organs of the tongue. The vagus contains a variety of 
fibres, both afferent and efferent, the former from the larynx and 
respiratory organs, the latter distributed to the organs of circulation 
and digestion. The spinal accessory has a characteristic distribu- 
tion to the cleidomastoid, sternomastoid and trapezius muscles of 
the side of the neck and shoulder. The twelfth, or hypoglossal 
nerve has the relation of the ventral or motor portion of a spinal 
nerve, and is distributed as a motor nerve to the muscles of the 
tongue. 
THE DIGESTIVE SYSTEM. 
The digestive system comprises as its chief portions the 
digestive tube and the digestive glands. The digestive tube is 
divisible into several parts, which, with the exception of the caecum 
and its vermiform process, are arranged in a linear series. The 
digestive glands comprise the oral glands, the liver, and the 
pancreas. They are parts of an extensive series of epithelial 
glands, otherwise contained within the wall of the tube, and for 
this reason not appearing as gross structures. 
