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Titre : Philosophical transactions of the Royal society of London. B

Auteur : Royal society (GB)

Éditeur : printed by Harrison and sons (London)

Éditeur : The Royal society (London)

Date d'édition : 1908

Type : texte

Type : publication en série imprimée

Langue : anglais

Format : application/pdf

Description : 1908 (VOL199).

Droits : domaine public

Identifiant : ark:/12148/bpt6k56064p

Source : Bibliothèque nationale de France

Relation : http://catalogue.bnf.fr/ark:/12148/cb34422226r

Relation : http://gallica.bnf.fr/ark:/12148/cb34422226r/date

Provenance : Bibliothèque nationale de France

Date de mise en ligne : 15/10/2007

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in a transverse border posterior to which is a clear area quite frec from noural <»est élément^ and at the same tiine possessing a very scanty mesodenn. "This clear area is ..bounded posteriorly by thé acustico-facial. ganglion and its pedicle. The ganglion itself appears as an oval dark patch lying at a relatively greater distance from the edge of the medullary plate than in the earlier neurular stage al ready described (figs. 73 and 74). Thé pedicle which connecta- the obliquely-pliiced oval ganglion with thé edge of thé medullary plate consists of a proliferating tract of cells. Just behind the place of attachment of the\ pedicle, the medullary plate appears .slightly, but distinctly, nairowed. Lying in a bay bounde,d mi;dinlly l.y the edge of this constricted portion of the medullary plate, laterally hy thé hinder part of the Ë. acustico-facial ganglion, and anteriorly by thé pedieie of this ganglion, there is visible; hyboth of the jïgs. 75 and 76, a more or less roun<lod area of only slight ̃ opacity: "'Chia .-is due to thé jpresènce hère of a more or lms circular patch of °' thickenedWface-ectoderm, conslituting the auditory plate." If référence be made. to Plate 9 bit, illustrating Hili- and M ahtin's paper (hr. rit.), it will be seen that in-their représentation of the sameembryo as thàt shown In our présent 75, the reference-line aud." ieads to the açustico-facia^ ganglion, which would thus seem to be' idèntified with the auditory platt». This, ]iov*wr, is -cleaily ""ari oversight, for that which they correctly figure in section (jrfrîg. T>. Hite 10) as 'auditory plate," is obviously situated 'close to the edge'of tin» medullary plate, and not so. far out as thé ganglion labelled "and." in Plate ÎT bis, The plane of the section, illustrated An their fig.' 6, Plate 10, Mes just behind~and thé section accordingly misses– thè posterior extfemity of thé acusfico-facial ganglion. In the earjier Spécimens Z and ZZ we saw that the acustico-facial ganglion was' `` situated tolerahly close .to.the.ëdge of the medullary .plate, with the deeper part of whose latéral edge it is in obvious continùity. But, even in that stage, the sections prove that, behind the neck or pedicle pf thé ganglionic thickenihg,- there èjtiste -a differentiated area.of thickened ectoderm representing thé Anlage of thé audïtofy plate. Behind thé auditory region in fig. 76 there may be recognised the. representative of the ganglionic plate which was indicated in the preceding phase as constituting the rudiment of the-glossopharyngeus-vagus nerve-complex {cf. also text-tig1. 15).This ganglionic plate is thin and impejfect, and is tolerably well "defined only anteriorly and laterally, these marginal portions constituting the thickest portions of the sub-ectodermal ganglionic cell-plate. The anterior inargin is contiguous to thé posterior edge of the auditory plate, and it is this anterior margin which on surface view is most plainly seen to be connected with the edge of the medullary plate. The almost equally definite lateral marginal portion of thé plate is coïncident with thé medial limit of thé pariétal zone" of embrypnic mesoderm, and indeed with the inner limit of the coelom, which already occupies the pariétal zone in this itspericardialregio.il (ç/1. fig. 96). R 2 .'̃̃