288 DISEASE IN WILD MAMMALS AND BIRDS 
this position is complete union and fusion, with the pro- 
duction of a single tube from the uterine fundus to the 
exterior, while in the lowest mammals, edentates and 
marsupials, the two Mullerian ducts retain their lateral 
position, and upon completion of embryonal life a double 
tube from the ovaries to the exterior is found. If the nor- 
mal fusion of the ducts does not take place, and if for any 
reason their proper relation is not reached, an abnormal- 
ity will result var^'ing according to the stage of 
development that has been reached. Thus in man instead 
of a single uterus of triangular shape and a single cervix, 
a double set of tubes may be found. It can be shown that 
the abnormalities of the human uterus are of definite and 
fixed types corresponding to an arrest of fusion or com- 
pletion of the developmental cycle as given for the 
Mullerian ducts and further that these very deformities 
are comparable to normal organs of lower orders. In 
other words abnoiTnalities in arrest of development in 
the human uterus represent normal types of lower uteri 
at various evolutionary stages. In monotremes there are 
two ovaries, tubes, uteri, cervices, a urogenital passage 
and a clitoris. This corresponds with Uterus didelphys 
"wdth a single vagina. This abnormality while occurring 
in the lowest mammal, does not represent the most 
marked deformity kno\\ni for the hmnan being — that in 
which the double tube remains to the vaginal outlet, a 
condition found in the marsupials. In this order the 
uteri are entirely separate, and each is fitted mth 
its own vagina. The next higher order, Edentata, seems 
somewhat out of place if it be judged by its female 
genitalia since it is possessed of a triangular uterus 
and single vagina but without distinct cervical seg- 
ment ; the tract is very similar to that of the Primates. 
Rodents, in the various families, present no uniform 
uterine construction, there being four kinds corre- 
sponding to as many degrees of Mullerian duct fusion 
and diiferentiation. The lowest forms simulate the 
