MORPHOLOGY OF THE HUMAN URINOGENITAL TRACT. 341 



of conditions which threw quite a novel h'glit ou the development 

 of the hjanen. I found that at the site of the hymen two 

 epithelial bulhs developed. These measured, in the specimen 

 shown at fig. 21, -3 mm. x '2 mm. ; as they near the middle line 

 they are larger, and they measure as much as -5 mm. x -4 mm. — • 

 i.e., may be double the former size. They He, in the main, 

 lateral to one another, are composed of epithelial cells exactly 

 like those of the adult vagina, and have their structure and 

 relations well shewn in fig. 21. The origin of these bulbs of 

 epithelium had now to be settled, and, on examining the sections 

 carefully, I at last came on the Wolffian duct ending in the 

 smaller one (fig. 21). This enabled me to clear up the matter, 

 as evidently these bulbs, which I now term the ' Wolffian bulbs,' 

 are derived from the Wolffian ducts, and as these, according to 

 all recent embryological work, are derived from the ectoderm ; 

 this layer is the source of the epithelium of the bulbs. The sec- 

 tions of this foetus further shewed that the epithelial cells 

 of these proliferated into the Miillerian vagina, mapped out the 

 fornices and passed into the lower third of the cervical canal, 

 blocking these up and rendering them solid for a time, as 

 Tourneux and Legay have well figured. 



The central cells, which, both in the Wolffian bulbs and in the 

 Miillerian vagina, are the more advanced, soon begin to des- 

 quamate, and in this way a central lumen forms. The view 

 advanced, however, by such able observers as jSTagel, Klein, and 

 Tourneux and Legay, requires careful consideration. Their view 

 is that the vaginal epithelium is the result of a transformation 

 of the original Miillerian lining, while I urge that we have an 

 actual eruption of cells from the Wolffian bulbs into the 

 Miillerian vagina : that indeed the mechanism is like what 

 I have described in the development of the prepuce and anus. 

 I would urge that the mere transformation of cells w^ould not 

 necessarily involve the coalescence that renders the vagina and 

 its fornices at first solid, while the explanation I have given 

 does. 



In order, however, to establish the opening of the hymen, an 

 active involution of epithelial cells in the urinogenital sinus takes 

 place, and thus by the distending bulbs above, and the epithelial 

 involution from below, the entrance of the vagina — i.e., the 



VOL. XXXV. (N.S. VOL. XV.) — APRIL 1901. Z 



