ABSTRACT
Frontal buds or pieces of the bill of duck and chick embryos have been explanted on the chorioallantoic membrane, transplanted as homo- or xeno-plastic grafts to the flank, the frontal bud and the limb bud of early host embryos, or associated as coelomic grafts with various isolated nerve sources. Results show that :
The onset of the histogenesis of Herbst’s and Grandry’s cutaneous sensory corpuscles is entirely dependent on the presence of a nerve ending, irrespective of the stage at which the graft is obtained. The nerve ending is also required for the maintenance of the structural integrity of the previously differentiated corpuscles and for their subsequent development.
Only somato-sensory nerve endings are able to ensure the development of the corpuscles ; central connexions are not required. Sympathetic or somato-motor fibres are not able to sustain the development of the corpuscles.
The corpuscle type, as well as corpuscle distribution, is in conformity with the origin of the integument in which it develops and is determined by the specificity and regional quality of the innervated dermal mesenchyme. The determination of the cutaneous territory occurs at a very early stage (prior to the 3rd day of incubation in the frontal bud of the duck).
Heterotopic or xenoplastic innervation of the graft between duck and chick does not alter the cutaneous specificity of the differentiation. However, corpuscles did not differentiate when duck frontal buds were innervated by mouse spinal ganglia.
These results are discussed in connexion with what is known about peripheric sense organs in vertebrates. A schematic model is proposed for the mechanism of the morphogenesis of the corpuscles.
Nous avons tenté de soumettre cette hypothèse à l’expérimentation en réalisant, en greffe cœlomique des associations de ganglions spinaux provenant d’embryons assez âgés (afin d’éviter la présence, dans le ganglion, de cellules non différenciées) et de territoires présomptifs de membres prélevés avant et après la migration des crêtes neurales. Bien que nous ayons obtenu un assez bon développement des membres, toutes ces expériences ont été négatives, les nerfs ne s’étant pas développés dans ces greffons non différenciés.
Les résultats des greffes hétérochrones (écart d’âge important entre le greffon et l’embryon hôte) seront analysés en détail dans une autre publication.
