. Quain's elements of anatomy . Fig. 650.—A SECTION through part op a bilaminar blastoderm of the cat. (E. A. S.) cct., ent., ectoderm, entoderm ; z.^h, thinned out zona pellucida. and columnar in form ; those of the lower being large and flat, as well describedby Hensen (98) and Schafer (No. 100). The mesoblast first makes its appearance in the course of the seventh day inconnection with the formation of the primitive streak, and according to KoUikeris formed entii-ely by proliferation of cells belonging to the epiblastic layer. Thiscellular multiplication takes place in an axial plate very s
. Quain's elements of anatomy . Fig. 650.—A SECTION through part op a bilaminar blastoderm of the cat. (E. A. S.) cct., ent., ectoderm, entoderm ; z.^h, thinned out zona pellucida. and columnar in form ; those of the lower being large and flat, as well describedby Hensen (98) and Schafer (No. 100). The mesoblast first makes its appearance in the course of the seventh day inconnection with the formation of the primitive streak, and according to KoUikeris formed entii-ely by proliferation of cells belonging to the epiblastic layer. Thiscellular multiplication takes place in an axial plate very similar to that previouslydescribed ia the birds egg, and the mesoblastic sheet which results extends in the Fig. Fig. 651.—Section op trilaminar blastoderm op the rabbit op eight days andNINE HOURS. (Kolliker.) ect., ent., as before; )ncs., mesoderm continuous in middle {pr.) with ectoderm. same manner forward along with the primitive streak from the margin of theembryonal area where their development begins. According to Kolliker the cells of the mesoblast have from a very early periodof their existence a marked spindle and stellate character, and in this respectdiffer obviously from those of the epiblast and hypoblast; and thus the sheet ofnew formation is easily recognisable both on surface views and in sections, as itexpands from its median attachment to the axial plate laterally over the surfaceof the germiual area. The sheet of mesoblast spreads out at first only to the sidesof the primitive streak and backwards, being widest behind ; but after a time italso extends fonvards in the form of two lateral plates which spread into theanterior part of the germinal area, in which previously the
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