654 SPECIAL HISTOLOGY. 



where the placenta is situated, before their walls disappear and their 

 cavity is thrown into that of the lacunae. In the venous trunks of the 

 gravid uterus, besides the circular muscular layer, with much enlarged 

 fibre-cells, which exist, also in other situations, I have found an external 

 and internal longitudinal muscular layer with similar colossal elements ; 

 so that here the increase of the walls may be directly demonstrated 

 ("Zeitsch. f. wiss. Zool." I. 84). 



208. Vagina and external sexual parts. The walls of the vagina, 

 1 line thick, consist of an external fibrous coat, a middle muscular layer, 

 and a mucous membrane. The thin white fibrous coat presents externally 

 a more lax, towards the interior a more dense connective tissue, with 

 numerous elastic fibres arid venous plexuses, and passes, without any 

 line of demarcation, into the second, redder layer, which, together with 

 connective tissue and numerous veins, contains, particularly during 

 pregnancy, a good many, developed, smooth muscular fibres, which, with 

 their transverse and longitudinal bundles of fibre-cells, O f 04, 0'08 of a 

 line long, constitute a true muscular membrane. The mucous membrane 

 is of a pale red color, with numerous larger and smaller folds and eleva- 

 tions the columnce rugosce ; it is composed of a dense connective tissue, 

 without glands, and containing elastic elements in extreme abundance, 

 to which its great firmness and extensibility are due. Its inner surface 

 presents numerous conical or filiform papillae, from 0-06 to 0-08 of a line 

 in length, and 0-025 to 0-03 of a line in breadth, which are entirely 

 imbedded in a tessellated epithelium, 0-07-0-09 of a line thick, of the 

 same kind as that in the oesophagus, the uppermost scales of which, 

 having a diameter of 0-01-0-015 of a line, contain nuclei of 0-003 of a 

 line. The hymen is a duplicature of the mucous membrane of the vagina, 

 and contains the same elements. 



From the vayina the mucous membrane is also continued upon the 

 external genitals, invests the glans clitoridis and the vestibule, with the 

 orifice of the urethra; folds of it constituting the preputium clitoridis 

 and labia minora. On the labia majora, it is continuous uninterruptedly 

 with the external integument, which, on their inner side, and at the 

 commissura labiorum, still bears a close resemblance to a mucous mem- 

 brane ; whilst on their border and outer surface, and on the mons veneris, 

 it resembles the cutis in all respects. The matrix of the mucous mem- 

 brane of the external genital organs, is a spongy, highly vascular, fatless 

 connective tissue, containing, however, a good many elastic fibres, and 

 which, in its condensed external layer, J-i of a line thick, correspond- 

 ing to the corium, is everywhere furnished with much-developed papillce, 

 in the labia minora 1-10-1-20, and on the clitoris 1-24-1-33 of a line 

 in length; and with a squamose epithelium of 0-04-0-12 of a line, the 

 most superficial cells of which are 0-01-0-02 of a line in size (Fig. 



