176 ' ANTHROPOLOGY. 
35 6, an exfoliating lens magnified, showing its tendency to divide into 
three segments. Fig. 36 a 8, iris, choroid, and pupillary membrane of a 
seven months’ foetus with their vessels magnified: a bc, choroid; d e, mem- 
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. ig. 41, do. the eyelids opened. J/g. 
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-g, lower eyelid; **”, muscles of 
the eye; ”””", optic nerve; ***, vessels and nerves of the eye; ™”, 
axis of the eyeball; **, its largest transverse diameter; **, centralis re- 
tine; *, sclerotic coat; *, pigmentum nigrum; “”*, choroid coat; ***, 
portion of the choroid uncovered by the retina; *°*’, iris; *”*, retina; 
“e* lens. fig. 43, horizontal section of the two orbits and of one eye: 
aa 8 8, frontal sinuses; y y, fat in the orbits: aad 4, section of the eth- 
moid bone; cc, dd, ee, ethmoidal cells; g, sella turcica; h h, section of 
sphenoid bone; 77, sheath of the optic nerve; £ £11, section of the zygo- 
matic bone; m m, section of frontal bone; 7 7, optic nerve; s, external, ¢, 
internal rectus muscle; wu, eyeball of the right side; v, do. of the left in 
section; w w, sclerotic; « x, the choroid; y y, cornea; zz 2 2, 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 
waich 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 Hyorpzs 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 
882 ; 
