File:A text-book of physiology - for medical students and physicians (1916) (14583782877).jpg

Identifier: textbookofphysio1916howe (find matches)
Title: A text-book of physiology : for medical students and physicians
Year: 1916 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Medicine
Publisher: Philadelphia and London : W. B. Saunders Company
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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anglion,which supply also themuscle of accommoda-tion, the ciliary muscle;while the dilator muscleis supplied by the longciliary nerves that arisefrom the ophthalmicbranch of the fifth cra-nial nerve, as representedin Fig. 135. The entirecourse of the motorpaths, preganglionic andpostganglionic fibers, isrepresented diagrammat-ically in Fig. 136. Themotor fibers to the ciliarymuscle and sphincterpupillse arise in the mid-brain in the nucleus oforigin of the third cranialnerve, and indeed in aspecial part of this nu-cleus lying most ante-riorly. They leave thethird nerve in the orbitand end within the sub-stance of the ciliary gan-glion, whence the pathis continued by sympa-thetic (postganglionic)fibers emerging from theganglion in the short ciliary nerves. The fibers to the dilator * For a physiological proof and the literature of the controversy seeLangley and Anderson, Journal of Physiology, 13, 554, 1892. For thehistological proof, Grunert, Archives of Ophthalmology, 30, 377, 1901.
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Course of constrictor nerve fibers,.Course of dilator nerve fibers,- - ■ Fig. 135.—Diagrammatic representation of thenerves governing the pupil (after Foster): II, Opticnerve; e.g, ciliary ganglion; r.b, its short root fromIII, motor oculi nerve; sym., its sympathetic root; rl,its long root from V, ophthalmonasal branch of oph-thalmic division of fifth nerve; s.c, short ciliarynerves; l.c, long ciliary nerves. 326 THE SPECIAL SENSES. muscle have a very different path. They arise also in the brain,most probably in the midbrain, although their exact origin hasnot been determined satisfactorily, and pass down the spinalcord to terminate in the lower cervical region. From this pointthe path is continued by spinal neurons which leave the cord in theeighth cervical and the first and second thoracic spinal nerves andpass by way of the corresponding rami communicantes into thesympathetic chain at the level of the first thoracic ganglion. Fromthis point the fibers pass upward in the cervic

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