The development of the human body; a manual of human embryology . to :&yJB. c Fig. 21.—Later Stages in the Segmentation of the Ovum of a , C, and Z? are sections, B a surface view.—(Van Bcneden.) 62 THE DEVELOPMENT OF THE HUMAN BODY. daily in those cells which are nearest what may beregarded as the lower pole of the ovum (Fig. 21, C),and these vacuoles, gradually increasing in size, eventuallybecome confluent, the condition represented in Fig. 21, D,being produced. At this stage the ovum consists of anenveloping layer, enclosing a cavity which is equivalentto the yolk-mass of the reptilia
The development of the human body; a manual of human embryology . to :&yJB. c Fig. 21.—Later Stages in the Segmentation of the Ovum of a , C, and Z? are sections, B a surface view.—(Van Bcneden.) 62 THE DEVELOPMENT OF THE HUMAN BODY. daily in those cells which are nearest what may beregarded as the lower pole of the ovum (Fig. 21, C),and these vacuoles, gradually increasing in size, eventuallybecome confluent, the condition represented in Fig. 21, D,being produced. At this stage the ovum consists of anenveloping layer, enclosing a cavity which is equivalentto the yolk-mass of the reptilian ovum, the vacuolizationof the inner cells of the morula representing a belatedformation of yolk. On the inner surface of the envelop-ing layer, at what may be termed the upper pole of theovum, is a mass of cells projecting into the yolk-cavityand forming what is known as the inner cell-mass, astructure comparable to the blastoderm of the one respect, however, a difference obtains, the innercell-mass being completely enclosed within the envelopingcells, w
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
