The class-book of anatomy : designed for schools, explanatory of the first principles of human mechanism, as the basis of physical education . ass. ANATOMICAL CLASS BOOK. 219 that the centre may not get without the axis of vision,is an envelope, having connexion with all the coats, wherethey are united on the borders of the cornea, and whereit joins the white part of the eye. Being equally trans-parent with the lens itself, it cannot be conveniently ex-hibited. Cataracts, the most frequent cause of blindness, origi-nate in the lens; sometimes half way between the centreand margin, hut ordinari
The class-book of anatomy : designed for schools, explanatory of the first principles of human mechanism, as the basis of physical education . ass. ANATOMICAL CLASS BOOK. 219 that the centre may not get without the axis of vision,is an envelope, having connexion with all the coats, wherethey are united on the borders of the cornea, and whereit joins the white part of the eye. Being equally trans-parent with the lens itself, it cannot be conveniently ex-hibited. Cataracts, the most frequent cause of blindness, origi-nate in the lens; sometimes half way between the centreand margin, hut ordinarily in the are eithera peculiar deposition of opaque or milky matter, entirelypreventing the ingress of light, or there is an opacity ofsome of the internal layers of plates, equally destructive tovision. Many children are born with this affection ; andat all ages, they are liable to form. To remove cataractsby extraction, the operator slides a sharp, thin knife, re-sembling a lancet, through the cornea, from one side tothe other, cutting one half from its natural attachment —leaving it in the form of a flap, thus: Fig. Explanation of Fig. plan represents an eye, surrounded by its natural appen-dages, with a knife passing through the anterior chamber. A dottedline indicates the lower edge of the flap, made by cutting offjustonehalf the cornea from its attachment with the sclerotica, in order to al-low the crystaline lens to escape, whenever the knife is withdrawn As a matter of course, the aqueous humor escapes in atwinkling, at the same moment, the capsule of the lenspreviously ruptured, designedly, by the point of the knife 220 ANATOMICAL CLASS BOOK. as it slides along, acts upon the lens by spontaneous con-traction, and protrudes it through the wound. Undoubt-edly the grasp which the straight muscles have on the ball,accelerates its escape Thus, in taking away the obstruction to sight, the wholelens is extracted. To couch, an operation often mention
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Keywords: ., bookcentury1800, bookdecade1830, booksubjectanatomy, bookyear1834
