176 ANTHROPOLOGY, 



35 5, an exfoliating lens magnified, showing its tendency to divide into 

 three segments. Fig. 36 a b, iris, choroid, and pupillary membrane of a 

 seven months' foetus with their vessels magnified : a b c, choroid ; d e, meni- 

 brana pupillaris; fg, long ciliary artery; ""^ vasa vorticosa of the choroid. 

 Fig. 37, the same figure nearly of natural size. Fig. 40, vertical section 

 of the left eye, the eyelids closed. Fig. 41, do. the eyelids opened. Fig. 

 42, outline references to the two preceding figures : A — H, upper wall of 

 the orbit ; M — Q, lower wall of do. ; R — V, dura mater ; w — z, forehead ; 

 a-d, eyebrows ; e-w, upper eyelid ; a-q, lower eyelid ; "" ", muscles of 

 the eye; "*"'*, optic nerve; "'"'•", vessels and nerves of the eye; "•", 

 axis of the eyeball; ", its largest transverse diameter; ", centralis re- 

 tinae; ", sclerotic coat; '°, pigmentum nigrum; '"""j choroid coat; "•"', 

 portion of the choroid uncovered by the retina; "■", iris; '""", retina; 

 *""", lens. Fig. 43, horizontal section of the two orbits and of one eye: 

 a a ß ß, frontal sinuses ; y 7, fat in the orbits : a ab b, section of the eth- 

 jnoid bone; c c, d d, e e, ethmoidal cells; g, sella turcica; h h, section of 

 sphenoid bone ; i ^, sheath of the optic nerve ; k k II, section of the zygo- 

 matic bone ; m m, section of frontal bone ; r r, optic nerve ; s, external, t, 

 internal rectus muscle ; u, eyeball of the right side ; v, do. of the left in 

 section ; w w, sclerotic ; x x, the choroid ; y y, cornea ; z z z z, coverings 

 of the eye. 



The remaining organ of sense, the tongue with its physiology, will be 

 more conveniently examined in connexion with the alimentary canal. We 

 proceed next to the consideration of the organs of respiration and voice. 



VI. ORGANS OF RESPIRATION AND VOICE. 



The larynx, trachea, and lungs, constitute an apparatus, by means of 

 wnich the oxygen of the atmosphere is introduced into the system and 

 carbonic acid gas is exhaled. They are at the same time adapted to the 

 production of sounds. We may even compare the lungs to the bellows of 

 a musical instrument, the trachea to the air pipe, and the larynx to the 

 tongue work. 



1. The Larynx. 



The larynx surmounts the upper extremity of the respiratory passages, 

 with which it communicates below as it does with the pharynx above ; it 

 is composed of a complicated apparatus of several cartilages, muscles, and 

 ligaments, which constitnte the organ of voice, and is suspended by muscles 

 and ligaments from the os hyoides. 



1. The Os Hyoides consists of five parts. The middle, or body, is con- 

 cave posteriorly and convex anteriorly ; on each side a cornu passes off, 

 giving attachment to muscles above and below; and where each cornu 

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