. Elements of comparative anatomy. Anatomy, Comparative. G16 COMPARATIVE ANATOMY. opens into the sinus urogenitals. The upper portion, which commences by a very wide ccelomic orifice, forms an oviduct (Fig 351, oc7), while the next and thicker-walled portion forms a uterus (u). Each of the two uteri open by a papilliform process into a portion, which from the exterior appears to be common to them both, and which is formed by the union of the two Mullerian ducts. A curved vagina is given off from this on either side (Didelphys), or the commencement of the tube is replaced by a caecal vaginal sa
. Elements of comparative anatomy. Anatomy, Comparative. G16 COMPARATIVE ANATOMY. opens into the sinus urogenitals. The upper portion, which commences by a very wide ccelomic orifice, forms an oviduct (Fig 351, oc7), while the next and thicker-walled portion forms a uterus (u). Each of the two uteri open by a papilliform process into a portion, which from the exterior appears to be common to them both, and which is formed by the union of the two Mullerian ducts. A curved vagina is given off from this on either side (Didelphys), or the commencement of the tube is replaced by a caecal vaginal sac which is pushed out backwards, and is usually, though not always, divided internally by a median partition ; from this sac the distinct "vaginal canals" (cv) pass in a curved direction to the urogenital sinus (cue/) (Halmaturus). In the monodelphous Mammalia the archincphric ducts are united with the Mullerian ducts to form a common chord (genital chord). The connection between the two Mullerian ducts, which is well marked in Halmaturus, is effected in them at about the middle point of the duct, and thus they become connected during embryonic life. A portion of these ducts have their cavities fused, while they are separate in front of, and behind this point; this is an indication of the common sac, which gives off the vaginal canals in the Marsupialia. But in the Monodelphia the lumina are fused as far as the end of the genital chord, and so form a single canal (genital canal) which opens into the sinus urogenitalis. There are, therefore, two canals, which are separated from one another at their commencement, but which unite into an unpaired portion of varying length ; these canals are derived from the Mullerian ducts, which are separate in the early stage of the embryo. The parts, which are distinguishable even in the Marsu- pialia, are due to the differences in the extent to which the walls of the different parts are differentiated, and the modifications in them a
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
