. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. THE SENSES 4 25 means of delicate ligaments. In front of the lens is a small cavity filled with a watery fluid, the aqueous humor, while behin<! it jg the main cavity of the eye, filled with a transparent, almost jelly-like, vitreous humor. The lens itself is elastic. This circumstance permits of a change of form and, in consequence, a change of focus upon the retina of the lens. By means of this change in form, or '^accommodation,''^ we are al^le to distin- guish between near and distan
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. THE SENSES 4 25 means of delicate ligaments. In front of the lens is a small cavity filled with a watery fluid, the aqueous humor, while behin<! it jg the main cavity of the eye, filled with a transparent, almost jelly-like, vitreous humor. The lens itself is elastic. This circumstance permits of a change of form and, in consequence, a change of focus upon the retina of the lens. By means of this change in form, or '^accommodation,''^ we are al^le to distin- guish between near and distant ol^jects. Defects in the Eye. — In some eyes, the lens is in focus for near objects,but is not easily focused upon distant objects; such an eye is said to be near- sighted. Other eyes which do not focus clearly on objects near at hand are said to be far-sighted. Still another eye defect is astigmatism, which causes images of lines in a certain direction to be indistinct, while images of lines transverse to the former are distinct. Many ner\'ous troubles, especially headaches, may be due to eye Diagram hHow- ing how the loiiH chanKc^ its Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George William, 1873-1948. New York, American book company
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