. The anatomical record. Anatomy; Anatomy. 122 GEORGE L. STREETER At one month the ear vesicle is completely differentiated into a membranous labyrinth with three semicircular ducts and a characteristic macular area to which is attached the gangHon and its peripheral nerve terminations. A characteristic endo- lymphatic appendage is present, consisting of a relatively large sac connected by a slender duct with the vestibular portion of the labyrinth. As can be seen in figure 9, the sac now Ues in close contact with the thin roof of the fourth ventricle. The labyrinth lies wholly dorsal to the m
. The anatomical record. Anatomy; Anatomy. 122 GEORGE L. STREETER At one month the ear vesicle is completely differentiated into a membranous labyrinth with three semicircular ducts and a characteristic macular area to which is attached the gangHon and its peripheral nerve terminations. A characteristic endo- lymphatic appendage is present, consisting of a relatively large sac connected by a slender duct with the vestibular portion of the labyrinth. As can be seen in figure 9, the sac now Ues in close contact with the thin roof of the fourth ventricle. The labyrinth lies wholly dorsal to the midlevel of the notochord and is secured in this position by the mesenchymal otic capsule,. Fig. 10 Diagram showing the migration of the ear vesicle relative to the brain wall from the position it occupies at the end of the second*,day (ot.) to the position it attains as a differentiated labyrinth at the end of the first month (of), the brain wall being represented as stationary. consisting of precartilage tissue, portions of which are already differentiated into typical cartilage cells surrounded by a homo- geneous matrix. With this stage the essential relations of the labyrinth may be regarded as established; the subsequent minor changes in its topography are those determined by the mechanical factors of its own further growth and the further growth and differentiation of the surrounding structures. From the foregoing comparison of the individual stages it is clear that the ear vesicle shifts its position relative to the brain wall to the extent diagrammatically shown in figure 10. ^Miereas at the end of the second day the vesicle lies ventral to and apart. 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 Bardeen, Charles Russell, 1871-1935, ed; Boyden, Edward A. (Edward Allen), 1886-1976; Bremer, John Lewis
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1906
