The American journal of anatomy . oved from any ectoderm. There is, andcan be, ii question as to their origin from entoderm. The budswhich are formed on the gill arches arc always on the inner surface,and there is no reason to doubt thai they arc formed from entodermcells as are those in the roof of the pharynx far removed from theectoderm. The buds which are formed in the vicinity of the teethare the ones which one might think would be derived from the in- The Limit Between Ectoderm and Entoderm. Gl growing ectoderm. The fact that this ectoderm forms dental ridgesdoes not wholly exclude the s
The American journal of anatomy . oved from any ectoderm. There is, andcan be, ii question as to their origin from entoderm. The budswhich are formed on the gill arches arc always on the inner surface,and there is no reason to doubt thai they arc formed from entodermcells as are those in the roof of the pharynx far removed from theectoderm. The buds which are formed in the vicinity of the teethare the ones which one might think would be derived from the in- The Limit Between Ectoderm and Entoderm. Gl growing ectoderm. The fact that this ectoderm forms dental ridgesdoes not wholly exclude the supposition that some of the cells mightgive rise to taste buds. Therefore, an account of the mode of forma-tion of taste buds in the front part of the mouth will be sufficient todetermine whether any of the taste buds are derived from 19 shows a taste bud forming in the floor of the mouth ashort distance behind the mandibular teeth at the time when themouth cleft is forming. The ectoderm is given a darker shade than. dmand. Fig. 19. A. punctatuin, sagittal section near the median plane shortly beforethe formation of the mouth opening. The section includes a part of the dentalridge in the mandible and the tip of the hyoid arch. Between the two is seena taste bud forming in the entoderm. The asterisk marks the caudal limit ofthe ectoderm of the vomerine tooth-germs. Iron hematoxylin, fuchsin. the entoderm and all the yolk granules are drawn. For a short dis-tance in the middle of the figure the nuclei are drawn. A small iso-lated opening indicates the forming mouth cavity. Below it appear agroup of elongated nuclei placed vertical to the floor of the grouping of nuclei is the first indication of a taste bud. Theoutlines of the cells are difficult to see on account of the great numberof yolk granules. This taste bud is forming in the entoderm betweenthe tongue and the teeth in the floor of the mouth. It is surroundedon all sides by entoderm crowded with yo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1910
