390 HISTORY OF THE HUMAN BODY 



terminal portions, and form a single vagina, though usually 

 with two lateral uteri, various stages of the fusion of which 

 form the successive steps known as uterus duplex, uterus bipar- 

 titus, and uterus bicornis. The first of these types possesses 

 two distinct openings for the uteri (ora uteri), which open 

 into a common vagina; in the others there is a single os, but 

 two uterine compartments. In all cases the vagina is single, 

 but an indication of its former duplicity is observed in a few 

 animals (e.g., Equus), in the form of a median longitudinal 

 fold. 



The duplex type occurs in Procavia (Hyrax), an iso- 

 lated group of small mammals found in Western Asia and in 

 Africa; the bicornis is widely distributed and occurs in ungu- 

 lates, cetaceans, most bats, and other forms; the bipartitus 

 occurs in carnivores, the pig, and a few bats. 



When several embryos are developed simultaneously, as in 

 most small mammals, the two uterine halves become drawn 

 out into long .tubes, and the embryos are fixed at approximately 

 equal intervals, each half containing about the same number. 

 As the embryos develop, the portions of the tube in which they 

 lie become greatly enlarged, while the intervening parts are 

 restricted, giving the whole the appearance of a necklace or 

 a string of sausages. 



The uterus simplex, characteristic of man and the apes, 

 represents the extreme degree of fusion of the two parts. In 

 this nearly all signs of its double origin are lost and the 

 uterus assumes the form of a balloon-shaped or piriform or- 

 gan, somewhat flattened dorso-ventrally, and possessing two 

 oviducts, which open at the slightly prolonged antero-lateral 

 angles. 



Uterus and oviducts are supported in all mammals by two 

 principal suspensory ligaments, the broad and the round (ligg. 

 latum et teres), which are easily explained by comparison with 

 the indifferent condition. [Plate III, a.~\ Here the two layers 

 of peritoneum that form the mesonephrotic ligament contain 

 between t%m the mesonephros and its duct, and become con- 

 tinue^ along the ventral surface of the mesonephros as a low 



