92 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
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S. SUMMARY ON THE DISTRIBUTION OF NERVES IX, 
X AND. XAT: 
These nerves contain viscero-sensory (red), viscero-motor (dark 
blue), and somatic motor (pale blue) elements. The viscero-sensory 
(red) are contained in [X and X, and reach their end organs by two 
nerves, (a) the pharyngo-laryngeal branch, coming off from XII, 
and (b) the visceral and recurrent rami of X. The sensory elements 
of the former appear to be distributed to the mucous membrane of 
the pharynx lateral and anterior to the glottis; those of the latter (not 
including those in the posterior visceral ramus) to the pharynx wall 
posterior to (a) and, through the ramus recurrens X, to the tracheal 
and laryngeal epithelium itself. 
The viscero-motor elements (dark blue) are carried in the pharyngo- 
laryngeal ramus of XII (excepting the fine motor fibers to the m. con- 
strictor jugulae) and may reasonably be assumed to be the same as 
those found in the coarse fibered roots of IX and X. They first give 
off fibers to the cerato-hyoideus muscle, then, after losing the sensory — 
elements to the pharyngeal wall, they form a partial crossing and each — 
has a bilateral distribution to the laryngeal muscles. Mig 
The somatic motor components (pale blue) comprise the three roots 
of XII. These differ from the somatic motor of the spinal nerves in | 
presenting collectively a much smaller-fibered nerve. A marked | 
exception exists however, in the third root, which possesses a cervical | 
part and a hypoglossal part, the two standing in contrast to each other | 
in size of fibers. The cervical part is distributed to the dorso-lateral 
longitudinal neck muscle. The hypoglossal part, combining with all | 
the components of the other two roots to form the main trunk of XII, 
innervates all the muscles of the ventral longitudinal series except — 
those extending from the girdle to the hyoid apparatus and the | 
cerato-hyoideus. | 
T. ADDITIONAL INNERVATION TO THE VENTRAL 
HEAD REGION. 
The other muscles of the ventral head region are supplied by V and © 
VII, thus indicating their visceral origin. Nerve VII innervates the - 
digastric and superficial constrictors, 7. e., sphincter colli and mylo- ! 
hyoideus in part; V innervates the mandibular series and all but the 
