The Development of the Hymen 



95 



Embryo If (Figs. 11-13). Fetus 21 cms. in length. The vagina is 

 seen to possess a lumen in its lower half, this lumen being filled almost 

 entirel}^ with desquamated epithelial cells, whose nuclei and proto- 

 plasm, though greatly shrunken, can still be differentiated. The three 

 layers of the vagina differ greatly in character from those described in 

 Embryos 1-3. The inner epithelial layer is here the thickest of the 

 three. The cells lie 12-15 rows deep and differ in size and staining 

 character in a way similar to that of the adult vagina; i. e., the super- 

 ficial cells are large, somewhat spindle-shaped, their protoplasm and 





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us 



Fig. 3. Median sagittal section tbrougli eutrauee of vagina into urogenital 

 sinus (Embryo 3). No fold is here visible. R., ventral wall of rectum; 

 U., urethra : Y., vagina ; U. S., urogenital sinus. Magnified 20 X. 



nucleus staining faintly; the deeper cells, especially the basal layer, are 

 small, cubical, with deeply staining nucleus and scanty protoplasm. Into 

 the layer of loose connective tissue cells outside this epithelial layer the 

 latter sends finger-like processes, so that at times apparent islands of 

 connective tissue cells are seen to lie in the midst of the epithelium. In 

 serial sections these can be seen to be continuous with the connec- 

 tive tissue layer. Judged by the pictures in the previous cases, it would 

 seem more rational to interpret this intertwining of connective tissue 

 and epithelial process as due to an outward growth of the epithelium 

 rather than an inward growth of the connective tissue. 



The inner connective tissue layer is not as wide but more dense than 

 in the embryos just described. The nuclei are smaller and stain more 

 deeply, and here and there beginning connective tissue fibrillae are to be 

 noted. The outer laver of connective tissue is not clearly differentiated 



