The development of the human body; a manual of human embryology . r becomes peri-chondrium and later periosteum; and the precartilageundergoes chondrification and later ossifies to form thepetrous portion of the temporal bone. The gelatinous layer completely surrounds most of theotocyst structures, which thus come to lie free in the peri- Fig. 246. — Transverse Section THROUGH A SEMICIRCULAR CaNAL of a Rabbit Embryo of Twenty-four , Periotic cartilage; ep, fibrous mem-brane beneath the epithelium of thecanal; p, perichondrium; s, spongytissue.—(Von Kblliker.) 468 THE DEVELOPMENT OF THE H
The development of the human body; a manual of human embryology . r becomes peri-chondrium and later periosteum; and the precartilageundergoes chondrification and later ossifies to form thepetrous portion of the temporal bone. The gelatinous layer completely surrounds most of theotocyst structures, which thus come to lie free in the peri- Fig. 246. — Transverse Section THROUGH A SEMICIRCULAR CaNAL of a Rabbit Embryo of Twenty-four , Periotic cartilage; ep, fibrous mem-brane beneath the epithelium of thecanal; p, perichondrium; s, spongytissue.—(Von Kblliker.) 468 THE DEVELOPMENT OF THE HUMAN BODY. lymphatic space, but in the cochlear region the conditionsare somewhat different. In this region the gelatinouslayer is interrupted along two lines, an outer broad onewhere the connective-tissue wall of the scala media isdirectly continuous with the perichondrium layer, and aninner narrow one, along which a similar fusion takes placewith the perichondrium of a shelf-like process of the car-tilage, which later ossifies to form the lamina Fig. 247.—Diagrammatic Transverse Section* through a Coil of the Cochlea, showing the Relations of the Scales. c, Organ of Corti; co, ganglion cochleare; Is, lamina spiralis; SM, scala media; ST, scala tympani; SV, scala vestibuli.—(From Gerlach.) Consequently throughout the cochlear region the peri-lymphatic space is divided into two compartments whichcommunicate at the apex of the cochlea, while below one,known as the scala vestibuli, communicates with the spacesurrounding the saccule and utricle, and the other, thescala tympani, abuts upon a membrane which separates itfrom the cavity of the middle ear and represents a portion THE MIDDLE EAR. 469 of the outer wall of the petrous bone where chondrificationand ossification have failed to occur. This membranecloses what appears in the dried skull to be an opening inthe inner wall of the middle ear, known from its shape asthe fenestra rotunda; another similar opening,
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
