. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 4§o Biology of the Vertebrates the vagina. The walls of the vagina are muscular and collapsible, and the muscular fibers near the external orifice form a sphincter. The outer part of the vagina constitutes the vestibule, which is separated from the vagina proper by a temporary fold of mucous membrane, more or less complete, called the hymen. This is the real end of the embryonic Miillerian duct, and it partially occludes the passage-way, particularly befor
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 4§o Biology of the Vertebrates the vagina. The walls of the vagina are muscular and collapsible, and the muscular fibers near the external orifice form a sphincter. The outer part of the vagina constitutes the vestibule, which is separated from the vagina proper by a temporary fold of mucous membrane, more or less complete, called the hymen. This is the real end of the embryonic Miillerian duct, and it partially occludes the passage-way, particularly before copulation has taken place. Originally in all mammals, the hymen persists in bears, seals, hyaenas, and most apes, but is present only in the young of the horse, pig and mole. The walls of the vestibule are supplied with erectile tissue which at times becomes surcharged with blood. In primates generally around the vestibule on either side are two folds of skin, the labia minora, while in the higher primates there are in addition two external folds, the labia majora, covered outwardly with pubic hair and supplied with a cer- tain amount of fatty tissue. There is also a pad of adipose tissue anterior to the vestibular orifice at the edge of the pubic bones. Likewise covered with hair, it is called the mons Veneris. It is better developed in the human females of civilized races than in those of more primitive types. The female bushman is remarkable for the hypertrophy of the labia minora, as well as for the enlarged posterior gluteal muscles, resulting in enormously prominent buttocks, or the condition described as steatopygy (Fig. 403). The clitoris in the female is homologous with the penis in the male. It is situated just anterior to the vestibular open- ing between the folds of the labia minora and consists of two corpora cavernosa that are erectile, but there is no corpus spongiosum present, and the clitoris is not traversed by the urethra like the male penis, except in a
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