. Text-book of normal histology: including an account of the development of the tissues and of the organs. ossesses delicate branched cellsas well as numerous blood-vessels,and corresponds to spft embry-onal connective tissue ; later thecorpuscles and blood-vessels dis-appear and the mass assumes itscharacteristic semi - fluid almoststructureless condition. The pe-ripheral zone of the vitreous un-dergoes condensation and formsthe hyaloid membrane, whichin the ciliary region becomes thick-ened and constitutes the suspen-sory ligament of the lens, or thezone of Zinn. The eyelids develop as folds
. Text-book of normal histology: including an account of the development of the tissues and of the organs. ossesses delicate branched cellsas well as numerous blood-vessels,and corresponds to spft embry-onal connective tissue ; later thecorpuscles and blood-vessels dis-appear and the mass assumes itscharacteristic semi - fluid almoststructureless condition. The pe-ripheral zone of the vitreous un-dergoes condensation and formsthe hyaloid membrane, whichin the ciliary region becomes thick-ened and constitutes the suspen-sory ligament of the lens, or thezone of Zinn. The eyelids develop as folds ofintegument above and below thecorneal area ; these grow towardsone another and finally fuse, allepidermal demarcation for a timedisappearing. Shortly b e fo r ebirth the centre of the epitheliallayer undergoes degeneration andthe lids become permanently separated. The epithelium of both the tegumentary and conjunctival sur-faces is derived from the ectoderm, as are also such epidermalappendages as the hairs and the glands, the Meibomian glandscorresponding to sebaceous follicles in their Section through developing eye of thirteen-day rabbit embrjO : e, ectoderm ; /, lens, con-sisting of anterior nucleated division repre-senting thin front wall of lens-sac and greatlythickened posterior division, completely fillingcavity of sac by elongated fibres whose nucleipresent crescentic zone («) ; /, posterior pig-mented layer; r, specialized anterior retinallayer; /, point where layers of optic vesicle be-come continuous ; ti, extreme peripheral sectionof tissue of primitive optic nerve connected withvascular tunic (v) occupying posterior surface oflens; m, surrounding mesoderm, which at tgrows between lens and retina. THE ORGAN OF HEARING. ,77 CHAPTER XVII I. THE ORGAN OF HEARING. The complicated organ of hearing of man and the higher animals,reduced to its essential factors, consists of two parts,—the system ofintercommunicating epithelial tubes, certain parts of who
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphiladelphiajblipp
